July09 by Astronomy Technology Today

ASTRONOMY

TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment

ASO’S INSTALLATION OF THE PLANEWAVE CDK-17 • THE SPIKE-A FOCUSING MASK UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO • THE CAMBRIDGE DOUBLE STAR ATLAS TAURUS TECHNOLOGIES’ DARK SKY ATLAS • THE BACKPACKING ASTRONOMER A PVC SECONDARY MOUNT ON A WIRE SPIDER • UPGRADING THOSE TINY TELRAD ALIGNMENT KNOBS

The PlaneWave Instruments CDK An Insider's View of the Origins of PlaneWave Instruments and Its CDK Telescopes

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Contents Industry News

Cover Story -31 PlaneWave Instruments’ 17-inch Corrected Dall-Kirkham (CDK17) is pictured with an SBIG STL-11000 installed. The background image of a portion of the Veil Nebula was captured by Johannes Schedler using a CDK17 and SBIG STL-11000 mounted on a 10 Micron GM2000 mount. The Veil image combines LRGB exposures of 20 minutes each. The 42-mm diagonal frames were essential to capturing the extensive Veil section without stitching and are indicative of the CDK17’s capacity to fully illuminate large format CCDs such as the 4008 by 2672 array of 9-micron pixels and huge image area of 36 mm by 24.7 mm of SBIG’s STL11000 cameras. As this Veil image attests, the CDK17 delivers pinpoint stars across the entire frame. The remarkable design of the f/6.8 CDK17 provides this level of optical performance with no off-axis coma, no offaxis astigmatism, and a perfectly flat field to the edge of the 52-mm image circle. PlaneWave CDKs are currently available in apertures of 12.5, 17, and 20 inches, with a 24-inch version anticipated at the end of this year.

In This Issue 12 Editor’s Note IYA and Other Reader Accomplishments By Gary Parkerson 31 The PlaneWave Instruments CDK An Insider's View of the Origins of PlaneWave Instruments and Its CDK Telescopes By Richard Hedrick 41 Arkansas Sky Observatories “A PlaneWave CDK-17… is far more capable of reaching fainter magnitudes and making enhanced studies beyond what even the Palomar 200-inch telescope could accomplish only 40 years ago.” By Dr. Clay Sherrod 45 Unihedron’s SQM-LE and Knightware’s SQMReader PRO How Good is My Night Sky? By Jack Huerkamp 51 Taurus Technologies’ Dark Sky Atlas A Tool for Finding Your Next Dark-Sky Observing Site By Gary Parkerson

55 The Backpacking Astronomer An Easy-To-Carry, Multipurpose Observing System for Hikers By Erik Wilcox 59 The Spike-a Focusing Mask A Masterfully Executed Bahtinov Mask By Craig Stark 63 The Cambridge Double Star Atlas I haven’t been this excited over the release of a print-version star atlas since Wil Tirion’s Sky Atlas 2000 in 1981 By James R. Dire. Ph.D. 67 A PVC Secondary Mount on a Wire Spider My ATM Solution For Suspending a Secondary By Dave Merritt 68 Astro Tips, Tricks, & Novel Solutions Upgrading Those Tiny Telrad Alignment Knobs By Steve Sands

15 ASTRONOMY-SHOPPE Offers Meade Classic LX200 Repairs 15 DEEP SPACE PRODUCTS Acquires HyperTune and LXD Sites 16 APM TELESCOPES Brings the Orion Optics U.K. OMC140 to the U.S. 16 IOTT PRECISION INSTRUMENTS Manufacturing Custom German Equatorial Mounts

17 OPT CORP To Distribute StarworksTeam Cooling Box MK1

18 LUNT SOLAR SYSTEMS Introduces New Doppler True Tuning Technology 18 ORION TELESCOPES & BINOCULARS Announces Addition of Bushnell Products 19 ASTRO DOMES Names Durango Skies as Authorized North American Distributor 22 MERLIN SCIENCE Offers Self-Paced Astronomy Course On-Line Astronomy TECHNOLOGY TODAY

Contributing Writers

Contents New Products

Dr. James Dire has an M.S. in physics from the University of Central Florida and a M.A. and Ph.D. from The Johns Hopkins University, both in planetary science, and is an associate provost and a professor of physics and astronomy at Gardner-Webb University in Boiling Spring, N.C. He has played a key role in several observatory projects including the Powell Observatory, which houses a 30-inch (0.75-m) Newtonian, rebuilding and installing an 8-inch (0.20-m) Alvin Clark refractor in a new observatory built for it at the Naval Academy, and was the initial director of the Coast Guard Academy Astronomical Observatory in Stonington, CT, which houses a 20-inch (0.51-m) Ritchey-Cretien Cassegrain telescope.

Richard Hedrick co-founded PlaneWave Instruments in mid 2006. Prior to that, he served as the Chief Technology Officer and former co-owner of Celestron. Mr. Hedrick led the team that created the NexStar line, NexStar GPS line, and the CGE line of telescopes, along with the SkyScout. He has been awarded numerous patents for telescope designs and algorithms. Mr. Hedrick is also an avid amateur astronomer, astrophotographer and telescope maker.

Jack Huercamp is the President of Jack’s Astro Accessories, the US and international distributor for the MallinCam Video Observational System and an authorized SkyShed POD retailer. He has been an amateur astronomer since 1968, is the former secretary and president of the Pontchartrain Astronomy Society, and is currently the ALCOR for the PAS. He is a professional Mechanical and Environmental Engineer and has spent over 36 years working for the Sewerage and Water Board of New Orleans and currently its Chief of Engineering.

Steve Sands is a business systems analyst living in Alton, Illinois, and a member of the St. Louis Astronomical Society and the Astronomical Society of Eastern Missouri. He has been interested in telescope building and astronomy since high school. His favorite telescope is a 20-inch f/4 Dob that he built with friends, but he is also an avid solar observer, utilizing h-alpha and calcium systems to keep tabs on our nearest star.

Dr. P. Clay Sherrod is an educator and researcher in earth and physical sciences, astronomy and archeology. “Dr. Clay” as his students knew him has devoted over three decades to the advancement of public knowledge and appreciation of the pure and applied sciences. Now retired, he operates the Arkansas Sky Observatory and continues private research and outreach programs. Dr. Clay has published hundreds of papers in scientific journals and publications worldwide and numerous books on archeology, meteorology and climatology, archeoastronomy, astronomy, and biomedical research (http://www.arksky.org/pubs.htm).

Craig Stark, Ph.D. is, by day, a professor whose research involves trying to pull faint signals out of noisy, moving images of people’s brains. By night, he is an amateur astrophotographer and operates Stark Labs which provides software to help users pull faint signals out of noisy, moving images of the heavens.

David Merritt has been an amateur astronomer since receiving his first telescope, a 3-inch reflector, at the age of 12. A geologist by day, he views the stars from his dark-sky home in Amargosa Valley, NV. He follows the "experiment and scrounge" school of DIY, and has enough projects to keep busy for the next 642 years, unless he starts something new.

20 ASTRO RUBYLITH Offers Counterweight Shaft Modification for Orion Atlas and Sirius 22 JMI Develops TNT for Sky-Watcher 12-Inch Dob 23 OPTEC Introduces Two New Products

23 VIXEN OPTICS Vixen AX103S “Quad” Refractor 24 HOTECH CORPORATION Adds 1.25- and 2-inch T-Adapters to SCA Line 25 UNIVERSAL ASTRONOMICS Newest Mount: The DwarfStar 25 ORION TELESCOPES AND BINOCULARS New 2-Inch Multiple 4-Filter Wheel 26 CAMERA CONCEPTS Arcturus Shroud for Solar Observing 27 ASTRO-PHYSICS Four New Products Simplify Mounting Scopes and Accessories

28 HUBBLE OPTICS Introduces 5-Star Artificial Star(s) 29 NORTHERN LYTE PRODUCTS Introduces Mount-n-View Tripod Pads

Erik Wilcox has been observing the sky for more than 20 years and recently started a new forum at www.starstuffforums.com. When he’s not viewing the sky, he sings and plays guitar in a rock band.

Astronomy TECHNOLOGY TODAY

29 CCD-LABS Announces 2-Inch Motorized Filter Wheel

The Supporting

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The Companies And Organizations That Have Made Our Magazine Possible!

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Astro Hutech www.hutech.com page 26, 40 Astro Physics www.astro-physics.com page 13, 36 AstroSystems www.astrosystems.biz page 38 Astrozap www.astrozap.com page 56 Bobs Knobs www.bobsknobs.com page 60 Camera Concepts www.cameraconcepts.com page 24 Catseye Collimation www.catseyecollimation.com page 54 CCD-LABS www.ccd-labs.com page 53 Celestron www.celestron.com page 30 Chronos www.chronosmount.com page 49

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ASTRONOMY

TECHNOLOGY TODAY

Volume 3 • Issue 4 July-August 2009 Publisher Stuart Parkerson

Managing Editor Gary Parkerson

Associate Editors Russ Besancon Karol Birchfield Jessica Parkerson

Art Director Lance Palmer

Staff Photographer Jim Osborne

Web Master Richard Harris

3825 Gilbert Drive Shreveport, Louisiana 71104 info@astronomytechnologytoday.com www.astronomytechnologytoday.com Astronomy Technology Today is published bi-monthly by Parkerson Publishing, LLC. Bulk rate postage paid at Dallas, Texas, and additional mailing offices. ©2009 Parkerson Publishing, LLC, all rights reserved. No part of this publication or its Web site may be reproduced without written permission of Parkerson Publishing, LLC. Astronomy Technology Today assumes no responsibility for the content of the articles, advertisements, or messages reproduced therein, and makes no representation or warranty whatsoever as to the completeness, accuracy, currency, or adequacy of any facts, views, opinions, statements, and recommendations it reproduces. Reference to any product, process, publication, or service of any third party by trade name, trademark, manufacturer, or otherwise does not constitute or imply the endorsement or recommendation of Astronomy Technology Today. The publication welcomes and encourages contributions; however is not responsible for the return of manuscripts and photographs. The publication, at the sole discretion of the publisher, reserves the right to accept or reject any advertising or contributions. For more information contact the publisher at Astronomy Technology Today, 3825 Gilbert Drive, Shreveport, Louisiana 71104, or e-mail at info@astronomytechnologytoday.com.

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Editor’s

Note

Gary Parkerson, Managing Editor

IYA AND OTHER READER ACCOMPLISHMENTS with brush and any other paint and surIt’s early June as I write this column face. Early this year Sayward wrote to say – midway through the International Year that she was working on a series of porof Astronomy (IYA). IYA has so far gottraits in celebration of the IYA and it ten little mention in these pages and that wasn’t until weeks later that I finally is something we plan to remedy before made it to her website, www.saywardstuthe end of this year. dio.com. There I found five amazing Because this publication focuses on portraits in the style that is uniquely astro-products and has too few pages to Sayward’s: Tyco Brahe, John Dobson, report all of the developments in this Neil DeGrasse Tyson, Fred Haise, and, of fast-paced industry, we are generally limcourse, the guest of honor, Galileo ited to its news items and feature articles Galilei. I’ve met a couple of those fellows to just that. Occasionally though one of and can attest that Sayward had captured you will request coverage of some each perfectly. notable accomplishment that doesn’t I wrote Sayward to congratulate her, directly relate to specific equipment or but after several subsequent exchanges services and we are happy to oblige. So realized I was missing something imporearlier this year ATT covered the amazing tant and called to find out what. It was accomplishment of a then 14-year-old only then that I learned that the caption Caroline Moore. “Portraits of Astronomers” over those In a subsequent issue we’ll feature five images was a clickable link to another remarkable accomplishment, another page and that there were not five this one directly inspired by the IYA and, but more than 50 portraits in her IYA coincidentally, also achieved by a dediseries. Now, having seen some of cated young lady who shares our love of Sayward’s work in person – each as rich astronomy and of its tools. Those of you in lovingly sculpted texture as visual who’ve followed this magazine from its detail – and realizing the days of intense beginning will remember that we origifocus it takes to create just one...well, nally concluded each issue with a profile to suddenly learn there were more than of one of its readers. We soon realized 50? Take a few minutes to tour Sayward’s that amateur astronomers are a too-modon-line gallery for yourself. If current est group – we literally had to badger you plans are realized, these portraits will into contributing photos and biograsoon be available as prints in very limitphies and eventually replaced the profiles ed editions, as well as in a coffee-table with the Astro Tips you more readily book. When you visit Sayward’s website, share. don’t miss You Bubble Headed Booby! and Our first profile victim was Sayward Andromedan Gothic – just for fun. Duffano, an artist and vintage scope colThere’s also a collection of DSOs and lector living in Gulfport, Mississippi. another entitled “The Solar System,” Sayward is a prolific painter who most some of the originals of which were often works with acrylic on canvas or exhibited at NEAF 2009. metal panels, but who is as proficient

But for this magazine, I would not have met Caroline Moore, Sayward Duffano, and the hundreds more of you whose knowledge, skill, and accomplishments are truly remarkable, even intimidating. Publishing a magazine that targets an audience as knowledgeable is, frankly, a challenge. We must be very sure of every fact and can even count on receiving astute and constructive criticism of grammar and composition from time to time. The fact is, because most of the content of this magazine is provided by its readers, it is a cooperative endeavor and we welcome and appreciate your participation. I was reminded today of another IYA inspired project with which I am assisting and that would benefit from your direct input. Like many, it is simple in concept, but difficult in execution. It envisions simple, modular astronomy lab/observatory facilities, with supporting lesson plans and workbooks, and funding for placement of these modest resources within reach of students throughout the U.S. If successful, it would also contribute to the growing list of astronomy resources available to students throughout the world via the Internet. One key to the project is that its lesson plans would relate the scientific processes of astronomy to every field of study, enabling, for example, budding visual artists to not only learn color theory, but to experience first hand the amazing physics of color, chemistry students to connect their studies to the magical alchemy of the stellar laboratories, and even journalism students to more effectively relate to, understand, and report technical fact. If in providing more students the opportunity of their own at-the-eyepiece revelations, we gain a few more enthusiasts and enable even more Caroline Moores and Sayward Duffanos, we all benefit. Iâ&#x20AC;&#x2122;m posting a draft of the project proposal on the ATT forum at http://tech.groups.yahoo.com/ group/astronomytechnologytoday/ and invite your input there. Meanwhile, clear skies.

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INDUSTRYNEWS

ASTRONOMY-SHOPPE Offers Meade Classic LX200 Repairs In news that is sure to make lots of Meade LX200 devotees very happy, Tony Costanzo, owner of the Astronomy-Shoppe of New Hampshire, has announced his company’s specialization in repair of Meade’s Classic LX200 telescope systems. Astronomy-Shoppe carries a full supply of replacement components for the main board, power panel, and declination boards of these popular telescopes. All repairs are performed by Certified Electronics Technicians and Engineers.

Electronics are tested as a complete system and all of the optical encoders are returned and calibrated correctly as a system. Those requiring repair of the electronics systems of their LX200 Classic telescopes need only ship the following parts to the AstronomyShoppe: power panel, power panel to main board ribbon cable, main board, RA motor assembly, Dec motor assembly, Dec cable, hand controller and cable, and power supply. Astronomy-Shoppe cautions that the main board should be completely wrapped in tin

foil for static protection. Cost of repair of electronics components will vary depending on vintage of the telescope and specific problems experienced, but generally start at $275. Because Astronomy-Shoppe stocks most electronic parts required for such repairs, it is generally able to return the repaired components within three weeks, although restocking of obsolete components may sometimes require additional delays. For more information, visit www.astronomy-shoppe.com.

escopes, we have seen our customer base grow as customers want to get the greatest possible performance from these scopes.” HyperTuning is one of the most popular services offered through the two websites. The process takes telescope mounts that are not performing to their optimum potential and tunes them to improve go-to slews as well as tracking for better astrophotography results. “We now see over 100,000 unique visitors to each website annually, a testament to the popularity of these scopes, and the interest owners have in getting the most out of their equipment,” said Harris who is also the owner of ScopeTrader.com and will continue to offer the ScopeTrader service to the astronomical community. The agreement is a perfect fit for Deep Space Products which was estab-

lished in 2007 to offer custom installation of its Deep Space Cooler, an add-on thermoelectric cooling system for the Meade DSI I, II and III camera systems. As part of the acquisition and reflecting the expansion of the HyperTune offerings, Deep Space Products is working with Harris to redesign its website and fold the offerings and content of the LXD websites into a single Deep Space Products website. Deep Space Products is currently working with Kelly Carroll of www.astro-rubylith.com to produce a new DIY HyperTune video for the popular Orion Atlas mount and will be offering in-shop HyperTuning and upgrading specific to the Atlas mount. For more information about these services please go to www.deepspaceproducts.com, www.LXD55.com or www.LXD75.com

DEEP SPACE PRODUCTS Acquires HyperTune and LXD Sites Ed Thomas, owner of Deep Space Products, has announced that his company has entered into an agreement with Richard Harris, owner of the websites LXD55.com and LXC75.com, to acquire the rights to the HyperTune products, services and websites, with plans to enhance and expand the product offerings and services currently provided through the two websites. This is a strategic move for LXD55.com and LXD75.com as it provides new facilities and support to customers of HyperTune telescope mount tune-up and related products and services. “Over the last several years, we have continued to see tremendous growth and interest in the products and services offered on our websites,” said Harris. “With the popularity and longevity of the LXD55, LXD75 and other GEM tel-

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INDUSTRYNEWS

APM TELESCOPES Brings the Orion Optics U.K. OMC140 to the U.S. APM America will soon be stocking the Orion Optics UK OMC140 MaksutovCassegrain telescopes. The new Maks combine the renowned quality of Orion Optics UK’s precision optics with a high-tech carbonfiber tube and are currently available in two configurations. The OMC 140C Mak-Cass features hand-finished and hand-corrected optics and a premium build quality to produce a telescope that delivers images of stunning visual and photographic quality. This is a Gregory Maksutov with an aspheric primary mirror producing image correction and quality that exceeds simpler Maksutov designs.

The carbon-fiber tube provides thermal stability, with optimal tensile strength to weight ratio. The 140-mm aperture Mak-Cass has a focal length of 2000 mm yielding a focal ratio of f/14. The tube measures 150 mm in diameter and 450 mm in length and weighs just 3.5 kg (7.2 pounds). It is guaranteed to equal or surpass 1/4 PV wavefront and features micrometer focusing and a fully collimatable system. Introductory pricing for the OMC 140C is $1,175US. The OMC 140C DL ups the ante with a minimum 1/6 PV wavefront, Orion Optics’ Hilux coatings, and a larger 50-mm finder. It is currently priced at $1,500US.

For more information, please visit www.apmamerica.com.

IOTT PRECISION INSTRUMENTS Manufacturing Custom German Equatorial Mounts We were first introduced to Kevin Iott of Iott Precision Instruments at NEAF 2009. Iott Precision Instruments is a new manufacturer of precision, custom German Equatorial Mounts and related accessories. The company currently offers two configurations of its mounts: the IPI 262 with a load capacity of 100 pounds and the IPI 393 that is rated to a capacity of 200 pounds. The Iott IPI 262 (pictured) features 6.6inch, 180-tooth gears precision crafted from 6061 Aluminum with stainless-steel matched and lapped worms driving 2-inch diameter shafts with built-in high-resolution encoders.

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The mount is delivered complete with Losmandy-format dovetail saddle and either Astro Electronic’s full-featured FS2 go-to drive system or the Sidereal Technology Servo go-to system. The mount features an 18-inch long, 1.875-inch diameter counterweight shaft and ships with one 15-pound and one 10-pound counterweight. The Iott IPI 262 mount is currently priced at $6,995US and is available packaged with a polar alignment scope and matching portable pier for a total of $7,995US. The Iott IPI 393 features 11.5-inch, 360-tooth gears that are also crafted from 6061 Aluminum with stainlesssteel matched and lapped worms driving 3-inch diameter shafts with built-in high-resolution encoders. Like the IPI 262, it is delivered with a dovetail saddle and either the Astro Electronic or Sidereal Technology go-to drive systems. It features a 24-inch long, 1.875-inch diameter counterweight shaft and ships

with one 10-pound and two 15-pound counterweights. The Iott IPI 393 mount is currently priced at $8,800US and is available packaged with a polar alignment scope and matching portable pier for a total of $9,800US. Iott Precision Instruments also sells premium counterweights precision machined from solid stainless steel, with bronze bushings and a unique 4-vane knob that operates a non-marring brass pin. Iott’s 40-pound counterweight measures 8 inches by 3 inches and is currently priced at $255US. Its 18-pound weight measures 6 inches by 2.5 inches and sells for $150US and its 10-pound counterweight measures 5 inches by 2 inches and is priced at $130US. Additional new products, such as Iott's unique weight-shaft accessory saddle, are planned, so be sure and consult its website, www.iottprecision.com, often.

INDUSTRYNEWS

OPT CORP To Distribute StarworksTeam Cooling Box MK1 In yet another NEAF 2009 announcement, OPT Corp. and StarworksTeam revealed their agreement for OPT’s exclusive distribution of the StarworksTeam’s Cooling Box MK1. The new product is the first patented, integrated solution for cooling DSLRs, while keeping the internal temperature constant throughout the entire shooting process. It promises to be the ideal tool for astrophotographers and deep-sky imagers who want to obtain the best possible performance from their DSLRs without any physical modification to those cameras, thus preserving the cameras’ original product warranty. The MK1 keeps the DSLR’s internal temperature constantly at the lowest possible temperature, or fixed to a user-

defined temperature, without alteration to the camera. Users are therefore able to minimize thermal noise of the system and can reuse dark frames from night to night, even when environmental conditions change radically. The system implements regulated thermo-electric cooling, a cooling method that has long been adopted for high-performance CCD cameras and those used for scientific purposes. Features and specifications include: (1) user defined temperature set point; (2) temperature delta (external versus camera body) from -20°C up to -25°C; (3) cooling case is sealed from the external environment; (4) environmental monitoring functions for temperature and humidity; (4) full bandwidth optical window with dewremoval system; (5) DSLR adaptable

cabling; (6) minimal-vibration dissipation and diffusion fans; (7) carbon-fiber cooling case to minimize weight; (8) symmetric physical configuration for best balance; (9) USB port for PC connection; (10) fan parameters are user configurable to minimize thermal flows; (11) software application provided for monitoring, control and setting all main system data; (12) aluminum handles for safe handling of the system; (13) protects the DSLR from contamination; and (14) available in several optional configurations. The StarworksTeam Cooling Box MK1 is priced at $1,499US. For more information, visit www.optcorp.com and www.starworksteam.com.

Astronomy TECHNOLOGY TODAY

INDUSTRYNEWS

LUNT SOLAR SYSTEMS Introduces New Doppler True Tuning Technology NEAF 2009 was our first opportunity to see samples of Lunt Solar Systems’ solar telescopes featuring its new Doppler True Tuning technology. This patent-pending technology advances the science of solar observing equipment to a new level. The new “tiltless” system encloses the etalon within a sealed cavity. The sealing is done via the collimating and refocus lens so that the etalon itself is isolated from differential pressure. A piston applies from zero to a pressure that is equivalent to taking an etalon from -500 feet to +12,000 feet above sea level, which essentially makes the etalon altitude insensitive. In addition, the etalon can be used from -50 to +200 degrees Celsius due to the fact that the tuning system also compensates for the very small changes that heat has on the etalon. By removing the need for tilt, Lunt has placed the etalon in the most optimized position possible and installs a precisely tuned etalon, tuned to the red side of the center wavelength. Because it is already tuned to the red, the user has the ability to shift the tune of the center wavelength to the Hydrogen-alpha line and then Doppler tune to the blue or back through to the red. Also, because there is no tilt involved, the image field remains flat and precise. Traditional tilting allows the Doppler

Astronomy TECHNOLOGY TODAY

shifting across the field in a plane perpendicular to the axis of light – the user can see a change in the image that allows the viewing of proms or filaments. True Doppler Tuning allows for a shift into and away from the user, adding a 3D component to the viewing experience. While it has minimal effect on proms due to their being at the edge, it does have an effect on filaments and active regions. While looking at a filament at the center of the Sun the user has the ability to Doppler shift from the base of the filament to the tip, following the filament through its structure. The True Tuning system provides an order of magnitude more precision to the tuning of desired features. Lunt is working on designs for its LS100F and LS100T/Na incorporating this technology and is currently manufacturing the LS60T and LS100T via this technology. Its existing LS60T is fully upgradeable to the new Pressure Tune System at any time, although this does require a return to the factory. Upgrade of in-stock LS60Ts is currently priced at $445US, while upgrade of those returned for installation of the system is priced at $495US. Overwhelming response to the new system at NEAF has translated into current upgrade delays of approximately 4 weeks. For more information, please visit www.lunt-solar-systems.com.

ORION TELESCOPES & BINOCULARS Announces Addition of Bushnell Products As part of Orion’s commitment to providing the widest possible selection of top-quality outdoor optics and equipment, it has announced its new Bushnell Product Center. Known for high standards and innovative technology, Bushnell is a premier manufacturer of quality outdoor optical equipment. Products currently available at Orion’s Bushnell Product Center include binoculars, spotting scopes, night-vision units, GPS units, and even a speed gun. Amateur astronomers will be particularly interested in several of the affordable, wide-field, long-eye-relief binoculars currently available from Bushnell. For example, its Legend 10x50 Binoculars are water-proof and fog-proof and combine eye relief of 17 mm with a wide 6.47-degree field of view. These rugged armored binoculars also feature fully multi-coated optics (with Raingaurd HD lens coatings) and BAK4 porro prisms, and weigh just 1.8 pounds. The Bushnell Legend 10x50 Binoculars are available from Orion for $199.95US. The full line of Bushnell products is available at Orion’s Bushnell Product Center by visiting www.oriontelescopes.com.

INDUSTRYNEWS

ASTRO DOMES Names Durango Skies as Authorized North American Distributor Dave Miller, owner of Durango Skies, has announced an agreement with Col Blumson of Astro Domes, to exclusively distribute Astro Domes products in North America. Durango Skies will provide sales and installation of all Astrodome domes. Based in Australia, Astro Domes products offer a revolutionary design which enables easy access through a rollover hatch, which then provides unobstructed viewing from zenith to horizon. Astro Domes has also announced that its Astrodome 3.0 meter Metal Kit Dome is now shipping and is available in both freestanding and semisphere (on structure) models. These domes give you the same precision-engineered, high-quality observatory that Astrodomes fiberglass line of domes is known for. The dome exterior is made of zinc/aluminium alloy coated steel panels that are bolted together and sealed with foam high bond tape. This exterior shell bolts to a

heavy-duty zinc/aluminium steel frame with steel rings and supports, resulting in a strong, secure and watertight observatory. The dome rotates on nylon support and guide wheels for a quiet and smooth operation, and is power by a 12v DC motor with a reversing switch. The watertight shutter rides on polyethylene strips and is also powered by a 12v DC motor. An external keyed entry switch allows the shutter to cover the entrance door for added security and waterproofing. Both models of the metal kit dome are available for an introductory price of $10,900, which includes shipping to any destination in the U.S. For more information, please visit Durango Skies (www.domeobservatory.com), Astrodomes authorized North American distributor. Durango Skies provides sales and installation of all Astrodome domes.

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DR. JAMIE LOVE/MERLIN SCIENCE Offers Self-Paced Astronomy Course On Line Dr. Jamie Love, who has taught a wide variety of science subjects from astronomy to zoology, is offering self-paced astronomy courses on the web. Free access to a sample of the first quarter of the course is available at www.synapses.co.uk/astro/contents.html. The remaining sections are included in a complete hyper-textbook. The course is divided into four quarters with 12 lessons in each.

After finishing a quarter, the student is encouraged to take a pair of exams: one tests understanding of the academic astronomy and the other the ability to identify specific objects. The course provides a wonderful introduction to the basic principles of astronomy for those who may be new to amateur astronomy and for high-school level students who want to explore the subject. Principles of Astronomy is priced at $40 for on-line download and a CD is available for $45, both with a full satisfaction guarantee. Give the sample quarter a test drive. Who knows, you might learn a thing or two. We did! Astronomy TECHNOLOGY TODAY

NEWPRODUCTS

ASTRO RUBYLITH Offers Counterweight Shaft Modification for Orion Atlas and Sirius

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Astro Rubylith has introduced a new modification for Orion Telescope & Binoculars’ Atlas and Sirius mounts that includes a 1-inch x 18-inch solid stainless steel counterweight shaft that incorporates a modified Declination axis nut. With its full 1-inch diameter, the modified counterweight shaft is more substantial than the retractable stock shaft and accepts any standard barbell weight that has a corresponding 1-inch bore. To take advantage of the modification, owners need only send Astro Rubylith the Declination axis nut to be tapped to the required threading (very simple for the owner to remove). Once the Dec nut is modified, Astro Rubylith will return it with the new counterweight shaft. The beefy counterweight shaft includes a new toe saver and an aluminum cover for storage. Astro Rubylith also offers locking collars for standard barbell weights. The price for the counterweight shaft modification is $121.99US and locking collars are $12.99 US. For more information, visit www.astro-rubylith.com.

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NEWPRODUCTS

JMI Develops TNT for Sky-Watcher 12-Inch Dob JMI’s Train-n-Track (TNT) system was widely successful when introduced for Meade’s Lightbridge series of portable Dobsonians – so much so that JMI has now developed a TNT system specifically designed for Sky-Watcher’s popular new Collapsible Truss-Tube 12-inch Dobsonian. The Train-n-Track system is a sophisticated, but simple-to-operate altitudeazimuth motor drive system with adjustable or "trainable" tracking. A simple 30-second training procedure allows the scope to track the target object for ten minutes or more without further input, thus freeing the user to enjoy uninterrupted views without the disruption of having to constantly bump the Dob to keep the target centered in the eyepiece’s field-of-view sweet spot. The TNT motor drives provide for adjustment of the speeds of both axes, highspeed centering, and one-touch reposition-

ing of the altitude tangent arm (current data indicates maximum slew rates of between 7 and 8 times for the 12-inch Meade LightBridge TNT application). The azimuth friction drive also allows the user to slew the scope by hand without unlocking any clutches – slew the scope and then just let go; the drive automatically takes over. With a little practice, objects can be kept in the eyepiece for 10 minutes or more, even at high magnification. The TNT unit includes a rechargeable battery with an AC adapter/charger. Installation is simple – you’ll be set up and tracking in very short order! Production models of this new TNT application will be available in the near future. For more information on the new Train-n-Track system for the Sky-Watcher 12-Inch Collapsible Truss-Tube Dob, please visit www.jmitelescopes.com.

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NEWPRODUCTS

OPTEC Introduces Two New Products Among the many new products we first discovered at NEAF 2009 were prototypes of two from Optec, Inc., that are destined to simplify the lives of small to medium observatory-class instrument users. Optec, located in Lowell, Michigan, has for many years been at the forefront of research and development of astronomical, visibility, and video/CCD microscopy optical instruments for both amateurs and professionals alike, and continues this tradition with the introduction of two new premium accessories. Optec's massive new Libra Alt-Az Adjustable Plate mounting base allows easy adjustment in altitude and azimuth of guide scopes mounted to a Losmandy-style dovetail system. Unlike simple 2-axis stage adjusting systems that only allow alignment of an imaging camera on a secondary scope, the Libra Alt-Az system allows easy

alignment of the entire secondary or guide scope’s optical axis to that of the primary telescope. Features include: (1) Fine control for adjustments in altitude and azimuth; (2) solid construction – anodized aluminum and stainless steel fasteners; (3) designed to fit any 4-inch dovetail system, featuring female-to-male mount for easy integration; (4) altitude adjustment of 5-degrees; (5) azimuth adjustment of 8-degrees; and (6) a payload capacity of an astounding 25 pounds! Optec's new 4-port Instrument Selector allows the remote observatory user the ability to remotely select any of four instrument packages attached to their telescope. The accompanying photo shows a top view of the selector carrying two different CCD cameras, a single-channel SSP photometer, and a separate TCF-S focuser and eyepiece, but an endless variety of instrument packages can be configured and used. A video demonstrating the 4-port selector on a Meade 8-inch Schmidt Cassegrain telescope is available from Optec's website, but it was specifically

designed for at least a C11 class telescope and intended primarily for permanent observatory instruments. The four instrument ports of the Perseus Instrument Selector consist of three 2-inch ports and one 3-inch port, all serviced by a 1/8th-wave first-surface elliptical mirror with a 3-inch minor axis. The embedded circuit has a single push button interface for use at the telescope and an RS232 DB9 interface for remote control. LED indicators show the currently selected instrument. The first production models of the instrument selector will be fully anodized and available from Optec by June 2009. For more information on both new Optec products, please visit their website at www.optecinc.com.

exceptionally flat field for sharp images to the edges of the field of view. “Precision Multi-Coating” are applied to all surfaces of the lenses to assure highest light transmission. The AX103S is manufactured in Japan and has a focal length of 825 mm. This new premium refractor also features as standard equipment Vixen’s new

dual-speed focuser that enables both coarse and fine focus adjustments. The new focuser can also be installed on Vixen's VC200, VMC200 and R200 Optical tubes. The AX103S refractor is accompanied with a five-year warranty and is priced at $2,999US. For more information go to www.vixenoptics.com.

VIXEN OPTICS Vixen AX103S “Quad” Refractor

Vixen Optics’ has introduced its new AX103S, f/8.0 refractor which features a three-element objective lens, incorporating a central ED lens. The optical design is optimized to reduce chromatic aberration and yield high-contrast images and incorporates a rear field-corrector lens (as diagrammed in the downstream section of the above ray tracing) to deliver an

Astronomy TECHNOLOGY TODAY

NEWPRODUCTS

HOTECH CORPORATION Adds 1.25- and 2-inch T-Adapters to SCA Line Hotech Corporation’s innovative SCA Laser Collimator earned a coveted spot on Sky & Telescope’s 2009 Hot Product list, larger because of its unique self-centering adapter (thus the designation “SCA”). That adapter assures that the collimator is installed securely and squarely to the telescope focuser, thus eliminating the possibility of poor collimation results due to corresponding misalignment of the collimator itself. Hotech recently introduced two new products that extend the unique benefits of the patent-pending design of its selfcentering adapter to astrophotographers as well: 1.25- and 2-inch SCA TAdapters. The new adapters self center loads perfectly in the telescope drawtube or visual back ensuring accurate, repeatable and secure installation for the best possible imaging results, regardless of tel-

escope design. The manufacturing tolerances of all telescope drawtubes require that they be of slightly larger diameter than the full range of eyepieces, diagonals and adapters that they may be called upon to accept. Hotech’s SCA T-Adapter accommodates and fills the inevitable space necessitated by these tolerances, resulting in accurate registration of the attached camera to the axis of the focuser. Locking the T-Adapter in the focuser is simple: push the adapter flush against the shoulder of the focuser rim and then twist the knurled compression ring clockwise. This expands the three evenly spaced synthetic-rubber compression bands (these are true compression bands) and locks the adapter firmly and squarely in the focuser. Removing the adapter from

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the focuser is as simple as turning the knurled compression ring counterclockwise. You need no longer worry about having to over tighten set screws to secure your precious camera load. The 1.25-inch SCA T-Adapter is currently priced at $45US and the 2inch version at $55US. For more information, please visit www.hotechusa.com.

CCTS CAMERA CONCEPTS & TELESCOPE SOLUTIONS

www.cameraconcepts.com At CCTS, the owners, Jeff and Greta, take a hands-on approach to customer service. Call them direct at 631-335-1279

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Arcturus Optics A CCTS Exclusive!

NEWPRODUCTS

UNIVERSAL ASTRONOMICS Newest Mount: The DwarfStar Universal Astronomics latest altazimuth mount is the ultra-compact and ultra-portable DwarfStar. This remarkably light-weight mount fits in the palm of your hand and tips the scales at just 1.0 pound, but is rated to carry a telescope load of more than 8 pounds. Setup is quick and easy and results in an amazingly stable foundation for your favorite travel scope. It is also completely waterproof and features tension adjustments on both axes. There’s even an optional eyepiece tray. The mount is designed to fit most pop-

ular camera tripods (3/8-16 thread), and at just one pound is capable of carrying 8 to 10 times its own weight. Its dovetail design accepts most narrow dovetail plates on the market as well as Universal Astronomics own Light and Medium Binocular Adapters. The optional eyepiece tray installs with a single clamp screw and can carry up to four eyepieces, of both 2-inch and 1.25inch barrels. Introductory pricing is $149 US. For more information, please visit www.universalastronomics.com.

ORION TELESCOPES AND BINOCULARS New 2-Inch Multiple 4-Filter Wheel Add yet another to the many astroimaging related products recently introduced by Orion. It's new 2-inch Multiple 4-Filter Wheel is essential to convenient tri-color (LRGB) imaging with largeformat monochrome CCDs and will accommodate Orion's 2-inch LRGB Astrophotography Filter Set. When it comes to field illumination for astrophotography, bigger definitely is better and Orion’s new 2-inch Multiple Filter Wheel allows convenient switching of up to four 2-inch filters for astro-imaging. Since many of today’s larger format monochrome CCD imagers require 2-inch filters for larger field illumination, this affordable solution

from Orion provides fast and easy transition between multiple filters. The versatile accessory provides for several attachment methods. T-threads on the telescope side allow for a direct connection to T-thread equipped focusers, or, if attaching the filter wheel to a standard 2-inch focuser, a 2-inch thread-on nose piece is also included, allowing maximum field illumination to the imaging camera. A removable T-thread ring on the camera side allows for direct attachment to imaging cameras. The new filter wheel is compatible with all 2inch Orion filters. This accessory is a must-have for monochrome imagers, who need to take

separate exposures through LRGB filters to obtain a color composite. Light finger pressure is all that's needed to rotate the wheel until the selected filter clicks into place. The 2-inch Multiple 4-Filter Wheel also provides a convenient and secure way to store your imaging filters and help protect them from dust and dew. Filters can be easily installed or changed by removing the cover with the included hex key. The filter wheel requires only 22 mm additional focus travel, weighs just 14 ounces, and is priced at $199.95 US. For more information, visit www.oriontelescopes.com.

Astronomy TECHNOLOGY TODAY

NEWPRODUCTS

CAMERA CONCEPTS Arcturus Shroud for Solar Observing One of our favorite solar observers, Barlow Bob, brought this new product to our attention. Bob’s Astro Tip for a home-brewed version will appear in a subsequent issue, but for those of us who aren’t tailors or seamstresses, Camera Concepts’ Arcturus Shroud is a very functional, cost-effective solution to the very real problem of protecting our eyes (and skin!) from raw solar radiation while enjoying views of our closest star. The use of a “photographer's dark cloth” greatly enhances visual observations of the solar disk – contrast is increased significantly and overall visual perception of detail is improved. Plus, the Arcturus Shroud works just as well to guard your dark-adapted vision against from intrusion of stray white light such as that from your neighbor’s

Astronomy TECHNOLOGY TODAY

porch light. The Arcturus Shroud is constructed of a durable, opaque black material on the underside and a highly-reflective, silver material on the outside to reduce heat and maximize contrast. This double-layered material is breathable to allow comfort underneath no matter how hot the temperatures becomes. Camera Concepts also incorporates a handy loop in the center of the shroud for easy hanging on any available handle or other part of your mount. Overall dimensions of the Arcturus Shroud are 32 inches by 44 inches, no more and no less than is required for the task, and it is priced at $39.95US. For more information on this and other Camera Concepts exclusives, please visit their website at www.cameraconcepts.com.

NEWPRODUCTS

ASTRO-PHYSICS Four New Products Simplify Mounting Scopes and Accessories A-P Eyepiece Projection Camera

Image 1

Achieve higher powers and closer images of celestial objects with AstroPhysics Eyepiece Projection Camera Adapter ($93US). The unit (Image 1) is a two-part adapter for use with your film camera, DSLR, or a CCD camera with a small chip. It is particularly handy for photographing the moon or planets. The adapter accommodates 1.25-inch eyepieces with maximum eyepiece housing height of 2.25-inch and a 1.5-inch maximum outer diameter. Shorter eyepieces with wider outer diameters may also fit due to the gradual taper of the internal diameter of the unit, from 1.7 inches to 1.52 inches. Some eyepiece experimentation may be required! This adapter is available as an individual part or preassembled with your camera-specific Tring for an additional charge. A-P Easy-Balance Saddle Plate for A-P Mounts Astro-Physics has redesigned its 16inch Dovetail saddle plate for use on all AP mounts. The new 16-inch EasyBalance Dovetail for Losmandy D-Series

Image 2

Plates ($210US) is now drilled with eight mounting positions. The plate (Image 2) allows easy balancing of frontor rear-heavy imaging systems by permitting the user to first offset the saddle

itself in whichever direction is appropriate for your instrument. Total inherent offset capability is 8.05 inches depending on how positioned on the mount. The smaller 1-inch knobs prevent interference with the declination motor box and can be locked with an Allen wrench for a secure hold. This plate accepts all Losmandy Dseries plates 12 inches or longer. The saddle plate features a ribbed design on its underside to eliminate unnecessary weight. A-P 2.7-Inch to Large Celestron SCT Adapter Adapting your Celestron SCT to use Astro-Physics accessories is a breeze with the new AP 2.7-inch to large Celestron SCT Adapter ($60 US). This threaded

Image 3

back (Image 3) allows the use of AstroPhysics 2.7-inch accessories with 11inch & 14-inch Celestron SCTs with the 3.25-inch rear cell. The accessory back was designed primarily to accept AP’s 2.7-inch PhotoVisual Telecompressor, but it will also work well with many other accessories. Combine it with a 2-inch adapter to achieve an unobstructed 2inch visual back. When used with the Astro-Physics 2.7-inch to 6x7 Outer Bayonet Adapter and either of the

STL Adapters for the Outer Bayonet, you achieve the maximum available light path to your STL Series camera and easy image framing. Virtually any accessory from 2.7-inch diameter on down in size can be used with this adapter, greatly increasing the versatility of your large Celestron SCT. A-P ADA671 and ADA672 Adapters Easy image framing and reduction of vignetting on large chip CCD cameras were the driving factors behind AstroPhysics’ design of these two new adapters (Image 4). The “Adapters to Attach SBIG STL Series to A-P Prime Focus Field Flatteners or STL, AO-8 or AO-L to the 2.7-inch to 6x7 Outer Bayonet Adapter” are available in two lengths: 1.58-inch (ADA671) for STL cameras with the 8-position color wheel, and 1.93-inch (ADA672) for STL cameras with the 5-position wheel. Correct lengths are crucial to maintaining critical spacing for pin-point stars when using Astro-Physics field flatteners. Radius-cut keyhole slots at the bolt attachment positions allow for safe attachment to the STL first, then mounting into position. Use them without a field flattener in conjunction with a variety of cameras and A-P adapters or in any light path that does not have rigid spacing requirements to achieve unvignetted images. Both sizes are $63US apiece. For more information on these useful new products, please visit www.astrophysics.com.

Image 4 Astronomy TECHNOLOGY TODAY

NEWPRODUCTS

HUBBLE OPTICS Introduces 5-Star Artificial Star(s) Many astronomy veterans consider the star test to be the ultimate procedure for verifying the optical characteristics and collimation of telescopes. But for most users, conducting a meaningful star test requires an accurately aligned mount with motorized tracking to keep the subject star precisely centered in the telescope field of view. Add to that the factors that real stars are simply not always available when it’s most convenient to test optics and that few observers want to spend precious time under clear, steady, dark skies star testing and adjusting a telescope that they’d rather be using for observing, and it’s easy to see why precision artificial stars have been so sought after. While an artificial star permits star testing without the drawbacks associated with real stars, a single artificial star is

Astronomy TECHNOLOGY TODAY

not always the right size for every scope of varying aperture and focal ratio or for every background lighting condition and distance between scope and target. Enter the innovative Hubble 5-star Artificial Star(s). As its name suggests, it features five bright white LEDs with five precision pinholes measuring 50, 100, 150, 200, and 250 microns respectively to enable the user to test practically any telescope from any reasonable distance and under a wide range of background lighting environments.

We do not suggest that you abandon other collimation methods with which you are already comfortable and proficient. But the star test is one of the best tools available to the astronomer for confirming accuracy of those collimation efforts. If your scope is still not in accurate collimation after your current practice, the star test will quickly reveal that fact and assist in fine tuning the optical alignment. With the Hubble 5-Star Artificial Star(s) you will be able to instantly tell which of its five “stars” is best for your particular telescope and conditions – simply use the smallest possible star that still produces clear defraction rings when defocused. The device even allows you to further adjust the individual brightness of each of the five stars simply by twisting the LED retaining cap. It also comes with a magnetically attached mask for covering any 4 of the 5 stars, leaving only the size and brightness that is perfect for your application. A single Hubble 5-Star Artificial Star(s) can be order for $14.95US, plus $5US for worldwide shipping, and a 2unit pack is available for $29.90US, plus $6.50US shipped worldwide. For more information, please visit www.hubbleoptics.com.

NEWPRODUCTS

NORTHERN LYTE PRODUCTS Introduces Mount-n-View Tripod Pads If you’re like us, you find yourself setting up your favorite telescope tripod on a variety of surfaces from time to time. It might be the puncture-prone floor of your observing tent one night, followed by mountaintop rubble on the next outing, then the bare concrete of an observing pad at your club dark site, only to return it to its well-earned spot on the carpet of your office or den the day after. Each of these surfaces presents a unique challenge, but there is fortunately now a single solution to each and every one. Northern Lyte Products’ new Mountn-View Tripod Pads were originally conceived to protect the floor of owner Ken Smith’s Kendrick Observing Tent, but were quickly refined to provide for sure, stable, and safe footing on the full range of surfaces faced by astronomers at home and in the field. Ken soon realized that he had an opportunity to solve another nagging prob-

lem – tripping over tripod legs in the dark – and introduced a version of the pads that includes a built-in red LED as well. If you’ve erected a tripod on concrete with the hard leg tips in contact with that relatively smooth surface, you know how easy it is to cause a tripod leg to “chatter” across it with the slightest bump, ruining alignment. We’ve experienced the same frustration when having to set up on rocky outcrops or other hard surfaces. Mount-n-View Tripod Pads feature a stucco-pattern non-slip, ultra-grip material on the underside while holding the tripod foot/point firmly in the finely-machined indention of the 1-inch thickness of the white UHMW material of the main body of the pads. The switched red-LED light and supporting battery of the lighted version are recessed into the UHMW body

and trimmed with engraved metal plates. The large diameter of the pads – 4 inches – ensures a stable foundation on any surface, soft or hard. Best yet, these premium tripod pads are attractive enough to compliment your finest tripod, whether on display in your office or den, or at that next start-party outing. A trio of the lighted configuration is priced at $110US, while three of the nonlighted versions are available for $80US. For more information, please visit www.northernlyte.com.

CCD-LABS Announces 2-Inch Motorized Filter Wheel CCD-Labs new QMFW 5-position 2-inch format motorized filter wheel is positioned to be the most cost-effective motorized 2-inch color wheel available. It features ASCOM support, a simple RS232 interface and even includes a USB-to-Serial converter. The wheel housing is extremely thin, measuring less than 30 mm in total depth, requiring minimum back focus. Precision positioning of the filter ports is ensured by magnetic sensor and the unit includes a T2 camera interface with 2inch interface. The QMFW also includes a DC lighter jack with 2.5-mm power tip and an optional AC power supply is also available. CCD-Labs new QMFW filter wheel has an introductory price of $369.99US.

For more information, please visit their website at www.ccd-labs.com.

Astronomy TECHNOLOGY TODAY

The PlaneWave Instruments CDK An Insider's View of the Origins of PlaneWave Instruments and Its CDK Telescopes By Richard Hedrick

At PlaneWave Instruments we engineer and manufacture the Corrected DallKirkham (CDK) telescope. This is a wonderful optical design which provides beautiful performance across a large focal plane from a system of remarkably simple optical elements. The design utilizes an ellipsoidal primary mirror, a spherical secondary mirror, and a two-element lens group near the focal plane of the telescope as shown in Image 1. All of these components are optimized to work in concert in order to create superbly pinpoint stars across the entire focal plane. This is not simply a Dall-Kirkham with a corrector. Rather the CDK is an optical system of its own in which each component is optimized to work in concert with the others to best cancel spherical aberration, off-axis coma and astigmatism, and to create a flat field.

Image 1: The layout of the CDK telescope.

CDK History The path by which the CDK design came to be is an interesting one. There may be others who have independently come up with this optical design, but I will tell the story of how the CDK was discovered for PlaneWave Instruments. The first design was made for visual use as a hobbiest project.

In 1991 a group of us started a telescope making class at El Camino College in Torrance, California, and quickly developed full-blown telescope making fever. Many great telescopes were made in the class, ranging in apertures from 6 inches to 28 inches, but eventually the core group of telescope makers in the class decided to make a large Astronomy TECHNOLOGY TODAY

THE PLANEWAVE INSTRUMENTS CDK class, Perry Hacking. Perry wanted to build a really big telescope for visual use and wanted to do it all by hand. Of course, we spent a great deal of time talking about what the perfect size telescope would be. The question eventually came down to how big of a telescope we could fit into two standard-size pickups, versus what was the largest amateur-made telescope that we knew of at the time: a 41-inch Newtonian. So naturally we decided to make ours “1” bigger, a 42inch Newt. It didn’t hurt Image 2: First light for the CDK 42-inch Dobsonian that “42” was also the antelescope in front of PlaneWave Instruments. swer to “the life, the universe, and everything” in telescope. This group consisted of Joe the popular series, The Hitchhikers Guide to Haberman, Jason Fournier, Don Quok, and the Galaxy. me, and was lead by the professor of the

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The problem with a big Newtonian is that the ladder required can be frighteningly tall, especially when used in the dark. So we thought of making a very fast Newtonian – f/3.3. The problem in turn with such a fast Newtonian is off-axis coma, so we started looking at correctors for the Newtonians and eventually settled on a Wynne corrector similar to that used by Palomar. That was our starting point and we optimized the design for our system. In April 1998 we placed an order for a light-weight 42-inch Pyrex mirror blank. Since we were associated with a college we got a good deal on the blank, but that also meant getting knocked back in the line for delivery – all told, it took 4.5 years to get the blank. Meanwhile, we had concluded that it would be too difficult for us to make the corrector lenses as Wynne correctors feature some very thin lenses with extremely short radii. Then a local amateur telescope maker, Dave Rowe, happened by. Dave lived nearby and had heard of the telescope mak-

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THE PLANEWAVE INSTRUMENTS CDK ing class. One evening, while dining at the Mexican restaurant across from El Camino, Perry explained our efforts to Dave and on the way out, Dave asked whether we had considered a Cassegrain. Perry explained that the secondary mirror of a Classical Cassegrain was too difficult for us to make – Perry said he found it scary (and still does) – so Dave asked about a Dall-Kirkham and Perry concluded that the off-axis performance of that design was too poor. The next weekend Dave was back again, asking suspiciously leading questions, as if an idea was brewing. One question Perry particularly recalls was: “If you were to place a corrector in front of the focal plane of a Dall-Kirkham, where would you guess would be the best place?” Perry ventured that something around 200 mm seemed a good trade between surface curvatures and the diameters of the elements, at which point Dave revealed that he had an idea to make a fairly simple corrector for a D-K. Perry recalls being very excited at the idea.

At the next weekly meeting, Dave delivered the optical prescription. Apparently Dave already had a basic design he had originally come up with back in 1996 and had optimized it for our project. The result was an incredible design that gave wonderful off-axis performance from lenses that were nevertheless relatively easy to make, and with the aid of a tertiary mirror the eyepiece would only be about six feet off the ground. Eureka! The CDK was born and Dave became a member of the team. The CDK 42 is only now being completed. By the time we'd finished the optics, everyone’s lives had gotten busy (kids, work, etc) and so the telescope sat for many years. Only recently, in April

Image 3: The prototype CDK18 made by Celestron. Pictured are Bob Peasley, mechanical engineer, Joseph Lupica, President of Celestron, and Richard Hedrick, then VP of Engineering at Celestron. The photo was taken in 2003.

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THE PLANEWAVE INSTRUMENTS CDK of 2009, did we finish putting it together and perform the first star test (Image 2). During the grinding and polishing of the 42-inch primary, we had a lot of time to talk about “the perfect imaging telescope,” and Dave Rowe and I discussed possible designs for a flagship telescope for Celestron where I was then VP of Engineering. After much brainstorming, I brought the idea to Celestron and it was decided that it would make a prototype CDK. The first one we constructed was the 18-inch seen in Image 3. After more planning and strategizing with the sales and marketing departments, as well as with Celestron’s distributors, we decided on production of a 20-inch CDK. At that point, Celestron hired Joe Haberman, the best mirror maker in the telescope making class, who had also by then started a small optics company called Haberman Optics. After Celestron's announcement of the C20 and shipment of two units, several events culminated in the conclusion that it no longer made sense to produce the telescope. Joe and I were, of course, extremely disappointed – it was such a wonderful design and we knew it was only a matter of time before others produced the telescope. During this time the company was sold and the C20 was officially dead. Celestron's president and I discussed the possibility of my independent production of the C20 since Celestron no longer wanted too. Furthermore, a university had placed an order that Celestron would not be able to fill, so Celestron gave Joe and me permission to produce the telescope needed to fill that order. That was the beginning of PlaneWave Instruments. Within six months, Joe and I left Celestron to pursue PlaneWave full time. Celestron was gracious enough to convey the drawings of the C20, now called the CDK20, so we didn’t have to start from scratch. Thank you to Joe Lupica, President, and to David Shen, owner of Celestron – both have been very supportive of our new venture. CDK Performance PlaneWave Instruments currently manufactures the CDK in three apertures: the

34 Astronomy TECHNOLOGY TODAY

Image 4: Shown are a spot diagram and diffraction simulation for the CDK20. The performance 21 mm off-axis is 6 micron rms spot sizes. 21 mm off-axis is the corner for a full-frame CCD.

CDK20, the CDK17 and the CDK12.5, with apertures of 20, 17 and 12.5 inches respectively, selling for $32,500, $22,000 and $9990. There has been a lot of talk about naming telescope designs and I want to be accurate with ours. We call it a CDK – short for “Corrected Dall-Kirkham.” But in truth, this is not simply a Dall-Kirkham with a corrector added. While, the design does start as a Dall-Kirkham, to which a lens group is added near the focus, it is then optimized – the system is optimized as a whole. It might be more accurate to call it a “Modified Corrected Dall-Kirkham,” but “MCDK” seems like a bit much.

Spot Diagrams With any high performance telescope, I consider it important to demonstrate optical performance with meaningful spot diagrams and Figures 4 through 6 provide those for the CDK12.5, the CDK17, and the CDK20. These spot diagrams are shown in three wavelengths and are for a flat field. The spot diagrams are presented on the right side of each figure and diffraction simulations on the left. The small squares are 9 by 9 micron – the same size as a typical CCD pixel. The spot diagrams show how light travels through the optical design if behaving as a ray and the diffraction simula-

THE PLANEWAVE INSTRUMENTS CDK

Image 5: Spot diagram and diffraction simulation for the CDK17. The performance 21 mm off-axis is 6.5 micron rms spot sizes. 21 mm off-axis is the corner for a full-frame CCD.

Image 6: The spot diagram and diffraction simulation for the CDK12.5. The performance 21 mm off-axis is 12 micron rms spot sizes. 21 mm off-axis is the corner for a full-frame CCD.

Astronomy TECHNOLOGY TODAY

THE PLANEWAVE INSTRUMENTS CDK

Image 7: Image of NGC7331 taken with a CDK12.5 and an SBIG STL11000 camera. This is a single 600-second image that has been dark subtracted and flat fielded. The image is 42 mm on the diagonal and is meant to show the pinpoint stars across the entire field.

tions demonstrate how the optical design performs if you treat light as a wave. Both are useful tools in understanding how a telescope will perform. But spot diagrams can be misleading. Many companies demonstrate spots of only one wavelength making it impossible to tell

Image 8: Blow up of the upper left-hand corner of Image 7 showing the pinpoint stars 21 mm off-axis of the CDK telescope.

how it will perform under different wavelengths. Some diagrams also hedge bets by showing performance for a curved field. If the telescope is to be used only visually, that may not be a problem because the eye can compensate for some amount of field curvature. But, if the telescope is used for im-

aging, then such reports can be misleading. If a telescope has a curved field, stars in the center will be in focus and stars at the field edges will be out of focus. If the spot diagram is displayed for a curved field, off-axis stars will look much better in the diagram than the system will deliver when imaging.

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THE PLANEWAVE INSTRUMENTS CDK Another way to hedge spot diagrams is to conceal the scale or spot size. Such a diagram may show a favorable comparison against a relatively poorly performing design, while not allowing meaningful comparison to high-performing designs for lack of meaningful spot scale. This is why we try to provide the fullest meaningful disclosure of our optical design. Our spot diagrams reflect performance on a flat focal plane and are shown in three wavelengths so you are getting the complete story. We also provide a scale to compare against as well as the RMS spot size of offaxis stars (typically the point of interest as on-axis spots are going to be limited by diffraction).

Image 9: An example of a 52-mm field of view taken with an Apogee U16 camera and a CDK12.5. On the left is a star near the center of the field and on the right a star near the lower left corner of the field 25 mm off-axis.

Image Performance So, in our efforts to explain the merits of the CDK design, we provide what we know to be meaningful spot diagrams. But, the more we show people these spot diagrams, the more we realize that they fail to convey the full story. We eventually con-

Astronomy TECHNOLOGY TODAY

THE PLANEWAVE INSTRUMENTS CDK cluded that showing actual results of stars on and off axis was a much better way to go (see the examples in Images 7, 8, and 9). Image 7 presents a full frame of NGC7331 – the field is 42 mm on the diagonal. Image 8 shows a blow up of the upper left hand corner of that image and demonstrates the pin-point stars produced at the edge of the field. Image 9 was taken with a CDK12.5 with an Apogee U16 camera that has a 52mm field on the diagonal. The image presents a star near the center of the field and a star near the corner of the field, again best illustrating the incredible performance of the optical design.

Image 10: M33 taken with an Apogee U16 with a 52-mm field corner to corner taken on a CDK20. Notice the perfect stars across the entire field. Image courtesy of Andre Paquette.

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PlaneWave CDK Features The PlaneWave CDK is not just a high performance optical design, it is also a wellengineered instrument. As explained earlier, the features start with the optical performance. The design has a flat, coma-free field, with no off-axis astigmatism over a 52-mm focal plane. The system is f/6.8 for the CDK17 and the CDK20, and f/8 for the CDK12.5. The CDK17 and CDK20 come with a 3.5-inch ID focuser that can be manually rotated 360 degrees, and the CDK12.5 features a 2.75-inch ID focuser which can also be rotated. Both focusers run on a lead screw so there is no slipping or movement as the angle relative to gravity changes. The primary mirrors are conical shaped and thus have lower thermal mass, so equilibration is fairly fast. The primary mirrors are glued to the mirror cell at the center of mass so no external torques act on the mirror as the gravity vector changes. The mirrors are also laser aligned to the mirror cell so their optical axes are true to the mechanical axis. This ensures that you won’t end up with a tilted field at the focal plane and makes collimation surprisingly easy for such a high-performance imaging platform. Since the secondary mirror is spherical, collimation is accomplished by tip-tilt of the secondary only. There is no need to go to great the lengths necessary to center the secondary over the optical axis of the primary as with an R-C design.

THE PLANEWAVE INSTRUMENTS CDK Nasmyth focus and with direct-drive motors and high resolution encoders on each axis. The CDK700 will be around f/6.5 and will also cover a 70-mm field of view. The directdrive motors have zero backlash and zero periodic and non-periodic error. This telescope is intended to bring the features and advantages of larger professional telescopes to a much wider market and we anticipate delivery of the first unit by the end of this year. I invite you to visit www.planewaveinstruments.com for regular updates on these and other new products.

Image 11: A portion of the Veil Nebula taken with the CDK17 and the SLT11000 camera. It combines LRGBs of 20 minutes each and is courtesy of Johannes Schedler. With a 42-mm diagonal, this image is another example of the full-field performance of the CDK design.

The CDK17 and 20 optical tubes use dual carbon-fiber trusses to minimize thermal expansion and contraction and to provide a light-weight, stiff structure. The CDK12.5 uses a closed carbon-fiber tube. And the large dovetail used to mount the telescopes features an expansion joint to allow for the different thermal expansion of aluminum versus the carbon fiber structure. These features, along with the benefits inherent to the CDK optical design, ensure that each PlaneWave telescope is a high-performing, well-engineered instrument.

What is New at PlaneWave PlaneWave Instruments is currently working on several exciting new projects, including a 0.66 reducer we are soon introducing that will work with the CDK12.5, CDK17 and CDK20. We also have a CDK24 under design that is probably about six months away from production. It will have a focal ratio of around f/6.8 and will feature more back focus than the current models. It will also cover an even larger 70mm focal plane. We are also working on an observatoryclass complete system designated the CDK700, a 0.7 meter alt-az CDK with

CAD drawing of the CDK700. This is a Nasmyth focus 0.7 meter alt-az telescope.

Astronomy TECHNOLOGY TODAY

Arkansas Sky Observatories’ Installation and Use of the PlaneWave CDK-17

“A PlaneWave CDK-17… is far more capable of reaching fainter magnitudes and making enhanced studies beyond what even the Palomar 200-inch telescope could accomplish only 40 years ago.”

By Dr. Clay Sherrod

At Arkansas Sky Observatories (ASO), founded in 1971, we have an array of telescopes ranging in size from good, portable Apochromatic refractors to a little-used 32-inch Cassegrain. The system’s four major observatory locations are in use pretty much 60 percent of all nights throughout the year, this being the average percentage of clear night skies. Efforts at these observatories concentrate on several key studies: (1) First and foremost are comets and comet morphology, with up to 30 comets studied and logged nightly; (2) astrometry of Near Earth Objects (NEOs) and typically concentration devoted to recently discovered earth-crossing objects for which the orbits are still very uncertain; (3) cataclysmic variable stars and novae/extragalactic supernovae; and, (4) planetary atmospheres, particularly those of Mars and Jupiter. As conditions in Arkansas and other once-rural areas continue to deteriorate

Dr. Clay Sherrod and the Arkansas Sky Observatories’ Mathis Instruments MI500 mounted PlaneWave CDK17.

in terms of nighttime sky steadiness, transparency and seeing, the idea of using larger telescopes reaches a breakpoint where the conditions can no longer

support larger aperture instruments. Up to a point I have always preached that “larger is better” in terms of telescopes of equal optical and mechanical quality. But Astronomy TECHNOLOGY TODAY

INSTALLATION AND USE OF THE PLANEWAVE CDK-17 worldwide, as the atmosphere surrounding us now supports more and more heavy molecular components, which hold and move heat and refractive waves, this trend is changing. Fortunately, recent technological advances allow us to conduct ever more refined research with telescopes of what was once thought to be modest proportions. Indeed, one of the telescopes that we use today – a PlaneWave CDK-17 (Corrected Dall-Kirkham) – combined with modern CCD and digital processing enhancements via a bank of computers and specialty programs, is far more capable of reaching fainter magnitudes and making enhanced studies beyond what even the Palomar 200-inch telescope could accomplish only 40 years ago. So the philosophy at ASO changed about 10 years ago to begin developing systems that relied on the very best resolution available from high-quality optics combined with custom digital enhance-

ments through computer means. We then assessed what our goals were, designed computer output needs for our programs and had those developed out of house, and began to pull in hardware resources that could match our goals – knowing full well that we were going to be limited by increasingly lighted and polluted Arkansas skies. Knowing that ASO was not moving to the arid southwest, the challenge was to adapt to provide the very best equipment to be used where we were destined to be. The PlaneWave CDK The remarkable PlaneWave CDK is, in my opinion, a work of art, both mechanically and optically. Constructed of virtually zero expansion carbon fiber and the finest machined aluminum fittings, the telescope provides hours of “focus free” operation throughout the rapidly changing nighttime temperatures of Petit Jean Mountain, where both summer and winter air temperatures can

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Astronomy TECHNOLOGY TODAY

drop as much as 50 degrees from sunset to dawn. The telescope is operated robotically via a computer system in the observatory’s office and once the Mathis Instruments MI-500 mount is initialized (we park the telescope in a predetermined position at the end of each night’s session) the operator need not enter the telescope room again until it is time to cap up the telescope and disconnect power and computer cables at the end of the night. The inability for moderate to large telescopes to maintain the plane of focus as the temperature changes is a very frustrating experience and even temperaturecompensating focusers cannot accomplish what a telescope constructed of carbon fiber can do in this realm. For the CDK, there are minor focus adjustments that need to be made from the heat of summer to the chill of winter – these amounting to less than one millimeter. But once the primary mirror has equalized to the temperature of the nighttime air, the focus for any given night will remain stable and not need any further adjustment with the CDK. The design of the Planewave CDK is so exacting that even the custom dovetail saddle plate is made with a combination of low expansion materials so that flexure during temperature changes do not affect the overall spacing of the telescope components. PlaneWave Instruments’ CDKs are outfitted with the fine Hedrick focuser, a design that prevents any possible axial slipping from the weight of heavy equipment; this focuser is provided with a remote focusing computer program that allows the user to make any small needed adjustments very easily from the PC screen; the total travel distance of this focuser is a very limited 1.5 inch, so it is important that the user position the focuser exactly midway at the initial setup to allow for the small extremes necessitated from summer to winter. I have found that adjustments of only

INSTALLATION AND USE OF THE PLANEWAVE CDK-17 0.05mm are adequate throughout the extreme temperatures of Arkansas nights. Such fine adjustments are a snap with the PlaneWave interface which displays the focuser position to within 1/100th millimeter with very repeatable accuracy. There appears to be virtually zero backlash in either direction with even the smallest correction to focus. To assist in rapid equalization of the primary mirror, three large and very silent/vibration-free fans can be operated all at once, or any one at a time, either manually or via a preset temperature thermostat that sets the fans in motion and shuts them off when equilibrium is reached. Optically, the PlaneWave CDK is the finest in the field. It is ideal for astrophotography because of its large, wide and very flat field of view, providing full-chip coverage of even the largest CCD cameras. The flat field and fast f/6.8 focal ratio were among the reasons that this telescope was selected for the ASO Astrometric Observatory building (Minor Planet Center H45). A true flat field is desirable for both astrometric and precise photometric measurements of asteroids and their motions across the sky; a custom astrometric measuring program at ASO allows for field stars to be selected and rejected based on residual placement in the field from any one of seven large star catalogs that fill one computer that is devoted entirely to providing star position data at the observatories. In designing the CDK, PlaneWave Instruments coupled modified DallKirkham Cassegrain optical primary and secondary mirrors with a revolutionary doublet lens that is located in the optical path inside the primary baffle tube; the light cone, focusing from the secondary, passes through this doublet and provides the field flattening and f/stop reduction necessary to the remarkable performance of the telescope. It is an incredibly accurate (and surprisingly effective) solution to the conventional long-focus

Cassegrainian design. I have measured light loss through this doublet and it is truly minimal, about that expected with a conventional “focal reducer,” but of far better quality and much larger aperture. However, even that fast f/6.8 configuration was still inadequate for the needs of the ASO Astrometric Program. PlaneWave is therefore developing a soon-to-be available 0/.66 reducer that will fit firmly into the Hendrick focuser to allow precise mechanical and optical alignment as they do with their series of camera and visual adapters – everything bolts to the back and nothing can “skew” from precise alignment. In lieu of the awaited Planewave reducer, I experimented and found that the Astro-Physics 0/.67 focal reducer placed at the proper spacing in a 2-inch barrel for our ST200 XM Class I monochrome CCD worked perfectly. It presents no vignetting, no image fall-off and no distortion nor coma whatsoever when

used with the PlaneWave and the ST2000 XM. This combination results in a focal ratio of f/4.7 overall and provides a perfect field of view for our astrometric requirements. The ST2000 XM has a pixel size of 6.4 microns however, which does not match well with this combination, but binning 2 x 2 provides an incredibly good match for optimal pixel size to maximize the system's potential resolution. The Mathis Instruments MI-500 GEM Without so much as a grumble, the large Mathis Instruments MI-500 German equatorial mount can handle the 125-pound CDK-17 and accessories with plenty of potential still in its back pocket. The specific MI-500 that we are using features a large bronze 13.1-inch worm gear and stainless steel worm driver. The optional solid bronze worm gear was selected due to its far greater resistance to wear over aluminum and in

Astronomy TECHNOLOGY TODAY

INSTALLATION AND USE OF THE PLANEWAVE CDK-17 recognition of our relatively constant use of the telescope and mount. We selected, and still believe it’s the best choice, Mathis Instruments’ option of the AstroPhysics GTO servo drive system with very large Maxxon high-torque motors and Swiss encoders in both axes of this large GEM. Four (4) 25-pound weights on the threaded DEC shaft are required to adequately balance the CDK in functioning mode. Balance is very easy – by loosening both clutches you can literally spin the large mount and telescope with mere toothpick pressure. We learned quickly however that the tracking on this mount is not as good if perfectly balanced, with a bit of “stictional shake” in the RA axis. To overcome this we simply have a quick-release bracket that carries a small 5-pound weight that can hang from either the counterweight shaft or the back of the large PlaneWave telescope dovetail saddle, whichever of the two positions is on the EAST side of the mount at any given time. One full week was spent drift aligning the system which sits on a massive seven-foot tall rectangular metal pier that alone weights 2,300 pounds. To attest to the accuracy of both the mount and the need for using drift alignment, this telescope will track unguided for as much as six minutes on a CCD image at f/4.7, this being more than enough exposure to capture faint asteroids and comets to 22 magnitude.

simply cannot access any of these covers. As for the Mathis mount and A-P servo system, a word of caution: all wiring going into the servo unit, as well as the cables from that computer into both the A-P hand box and the two drive motors, must be unplugged completely when not in use, as should the power cord. The system – I have learned the hard way – is quite prone to electronic damage from surges and spikes, whether from a thunderstorms miles away or the failure of a transformer on a nearby highway after being felled by an errant automobile. I don't mean to harp on what many would consider the relatively minor issues we have had with this equipment. Overall, our PlaneWave CDK/Mathis Instruments GEM combination deserves and gets an A++. As with any system there are going to be small things that might irritate or confuse, but I have never had the opportunity to operate such a complex, yet trouble free telescope system, from the largest observatory telescopes to those commercially made. And whether, as have many other current producers of premium telescopes, Rick Hedrick and Joe Haberman of PlaneWave decline to publish such easily misinterpreted “statistical test data” as Strehl ratio, surface figure, wavefront error or the like, I can attest to one simple fact: They don't have to – the performance and results speak for themselves.

A Few Issues As for downside issues, we learned quite early that the Mathis and AP servo combination simply cannot remember where the pier is – it performs a meridian flip quite well, provided that the target is far (i.e. about one hour of RA) on either side of the meridian. However, there can be frustrating moments attempting to acquire a target that is nearly overhead, within one hour east or one hour west of the meridian, and the operator must be careful to monitor at such times. We have even installed a small CCTV in the observing room so that we can watch the telescope near the meridian to better prevent pier collisions. Another major downside, particularly for southern USA observers, with the open-tube design of the CDK is that of dust and blowing pollen in the air which is prone to accumulate on the primary mirror surface as well as to falling onto the very hard-to-reach front surface of the lens doublet down in the baffle tube. PlaneWave offers an accessory “Spandex Shroud” that can be pulled tightly over the open truss of the CDK, but once on it can be difficult to remove or move to one side – something that is absolutely necessary to reaching the primary mirror’s protective cover as well as the Baggie-style covers over the secondary and baffle tubes. With the shroud fully installed, the operator

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Unihedron’s SQM-LE and Knightware’s SQM Reader How Good is PRO My Night Sky? By Jack Huerkamp

Although I bought my first “department store” telescope in 1968, I purchased my first real telescope in 1980 when I was 32. It was a Coulter CT100, a 4.25-inch f/3.5 Newtonian (Image 1) that collapsed into a small storage case, and I would bring it to my family’s weekend escape located 40 miles northeast of New Orleans. One night, I placed the scope on the ground while I looked for a clearing in the pine forest from which to get a better view of the sky. After locating one, I had problems finding the telescope – it was that dark on the property back then! Waning Moon II In 1976 I bought a house in New Orleans East, and in 1980 I constructed a 12.5-foot fiberglass domed observatory in the backyard, naming it Waning Moon. The skies were much brighter than those north of Lake Pontchartrain so I limited my observations primarily to the Moon, planets and bright deep sky objects. In 1988 I inherited the family property, sold the home in New Orleans, left the Waning Moon

observatory as I had no way to transport it, and moved to darker skies where I could again enjoy looking for faint fuzzies. However, I missed having a scope always ready to observe with so began planning for Waning Moon II. Having already experienced the “pleasure” of building a dome, I decided upon a roll-off roof design for my second observatory. During the planning process, I attempted to determine the limiting magnitude of the skies. The plan was to attempt to record the faintest star observable. I prepared a chart of Andromeda using SkyTools2 with stars to magnitude 6 labeled, and I took it and my red flashlight out to the site for the new observatory. I lay down on the ground, gazed at the constellation as it traversed the zenith and compared what I could see to the chart. I was able to see stars down to magnitude 5.1 Enter Hurricane Katrina When I prepared my yard for the observatory, I removed a minimum of trees to retain the

Image 1

forest and the light barrier they provided. My efforts proved to be a waste of time. On August 29, 2005, the eye of Hurricane Katrina passed over my property and, in a matter of a few hours, over 350 tress of all variety were blown down, uprooted or damaged to the point that Astronomy TECHNOLOGY TODAY

UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO bad news – the night sky of Waning Moon II was getting brighter. But by how much? When I observed the Little Dipper in 2008, I estimated that I could see down to magnitude 4.3 – a drop of almost a magnitude in less than 3 years. My skies were definitely changing. But so was I – I was getting older. So what was the true quality of my night sky?

Image 2

Image 3

they needed to be removed. In addition, my neighbors suffered similar losses to their trees – I could now see lights that I never knew existed. Added to the loss of the light barrier provided by the trees was the influx of Katrina flood-dis-

placed residents. Being unaccustomed to the relative security of country life, the first thing most of them did was install utility-company provided dust-to-dawn insecurity lights. Recent light pollution maps showed the

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DSRSG 2008 and the SQM-LE At last year’s Deep South Regional Stargaze I bumped into Gary Parkerson who was looking for someone to write a review on the SQM-LE by Unihedron and I quickly volunteered. The Sky Quality Meter - LE is an Ethernet-enabled SQM for night-time sky brightness monitoring. It is similar to the non-Ethernet versions of the meters sold by Unihedron, but instead of providing an instantaneous reading of the sky quality, it provides continual, connected measurements of sky brightness for astronomers in magnitudes per square arcsecond (MPSAS). Among its many uses are determining how good one’s night sky really is, documenting the evolution of light pollution in one’s area and monitoring sky brightness throughout the night, from night to night and from year to year. These are the functions that appealed to me the most. There are many other uses, such as being able to compare the sky brightness at different sites quantitatively, investigating how sky brightness correlates with the solar cycle and month-to-month sunspot activity, and for the CCD imagers establishing a correlation between the SQM reading and when the background reaches some ADC level. Unlike the hand-held SQM and SQM-L sold by Unihedron, the LE version does not produce a sky quality reading directly on the meter itself. Instead, it provides Ethernet connectivity and the output is observed on a computer. The device comes with applications for reading the data in Java, C, Perl, and Python. For the computer savvy reading this, they will understand what this means. The meter runs on 5 to 6 volts DC, via a provided 120-volt AC power adapter. Most purchasers of the SQM-LE will utilize the remote capabilities made possible via Internet using the provided Ethernet connectivity. However, it can also be set up locally to continuously monitor sky quality.

UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO The meter is designed for use with an Ethernet Hub or Switch and it comes with a 6-foot Ethernet cable. Since I had an open port on my wireless router, I figured I would first test the meter indoors. After reading the manual that came with the SQM-LE, I contacted Anthony Tekatch of Unihedron by e-mail for further help. He instructed me to install the Lantronix Device Installer that came on the supplied CD and then set up the IP address of the meter to one within the range of the router. I hooked everything up, applied power to the meter, and – nothing. As you might expect, this was due to operator error. I had set the IP address to one outside the range of the router. After another email to Anthony, and his quick response, I resolved the issue with the router settings – I was in business. The meter was communicating with my desktop PC via the router.

Image 4

Image 5

Enter Knightware’s SQM Reader The meter was sending data to the computer; but how was I to interpret it? Another email to Anthony provided the answers to my question. He answered that there were applications contained on the CD provided with the meter, but that the simplest SQM-LE interface software for Windows users was the freeware program SQM Reader by Knightware software. Anthony provided a link, and after a quick install, the meter was showing the sky brightness of my office in both magnitude per square arcsecond (MPSAS) and limiting magnitude (NELM) on the SQM Reader interface (see Image 2). Success at last! Since my observatory is not at a remote location, I did not need Internet connectivity to the SQM-LE – I only needed a crossover Ethernet cable to connect the SQM-LE to the Ethernet port on the laptop computer. A crossover Ethernet cable is not provided with the SQMLE as most purchasers of the SQM-LE will connect their meters to Ethernet hubs. Luckily I was able to borrow a 20-foot crossover Ethernet cable from a friend. I installed SQM Reader on my laptop and connected the meter to it using the crossover cable. Failure again! I was getting use to this, and e-mailed Anthony for what seemed the hundredth time (he is a very patient individual). Anthony diagnosed the problem as with the way my laptop’s Local Area Connec-

tion was configured, provided a suggested IP address, and once I followed his directions, the SQM-LE was providing data to the SQM Reader interface. So now I knew how bright the inside of my home was. But what was the quality of my night sky? Deluxe Meter Setup I was anxious to get the meter outside, so I quickly devised a test setup. I drove a 1-inch by 2-inch stake into the ground at a slight angle from the vertical so the roof or side of my house would not affect the readings the meter would provide. I attached the meter, power supply and cables to the stake using rubber bands and protected the meter from the elements with a baggy,

being careful to not place the crease in the bag in line with the lens. I routed the 20-foot crossover cable from the meter to the laptop PC in my living room through a gap in the sliding glass door, started SQM Reader, and clicked on “Read Now.” SQM Reader’s screen indicated a sky quality of 8.04 MPSAS or -5.6 NELM. This first sky test took place beginning at 5:05 pm CST on November 13, 2008. Sunset had occurred at 5:04 pm, and twilight would not end until 6:26 pm CST, which accounted for the terrible sky quality readings provided by the meter. Also, November 13, 2008, was the night of the full moon, so my night sky would never be completely dark. Astronomy TECHNOLOGY TODAY

UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO

Image 6

I set SQM Reader to poll the meter every 15 minutes, and let the program run until 6:05:49 am the next morning. The data readings were saved in a text file (see Image 3). Data is nice, but everyone likes pretty pictures. How could I convert the data into one? Anthony provided the answer in another e-mail. All that I needed to do was (1) Open Microsoft Excel, (2) Select “File,” (3) Select “Open,”

SkyWatcher Telescopes

(4) Select “Text Files” from the “Type of Files” Menu, (5) Select the SQMLE File that you want to open, (6) Run the “Text Import Wizard,” (7) “Delimited” should already be selected – if not, select it, (8) Click “Next,” (9) DeSelect the “Tab” Delimiter, (10) Select the “Comma” Delimiter, (11) Press “Next,” and (12) Press “Finish.” Did you get all that? If so, you have successfully converted the readings from the SQM-LE into a graph, such as that derived from data obtained the night of November 13-14, 2008, shown in Image 4. To the data file provided by Knightware’s SQM Reader, I added the Moon’s altitude. As seen on the graph, the best sky quality occurred at about 6:05 pm – before the end of astronomical twilight, but with the full moon only about 10 degrees up in the east behind the trees. The meter provided a reading of 18.48 MPSAS and SQM Reader converted that to a limiting magnitude of 4.4. By 12:50 am on the 14th, the full moon was high in the

sky and the SQM-LE was aimed directly at it. The sky quality at this time was only 14.18 MPSAS or 0.5 NELM. Also seen in the graph are random dips and rises in the MPSAS readings provided by the meter. This was due to passing clouds reflecting back the light pollution. This first night was successful in showing that the meter worked. But it did not show me how dark my sky was on a moonless and cloud free night. The moon would not be new for two weeks to run a full night’s measurement of sky quality. However, weather conditions on November 16 were perfect – it was cool and the sky was clear and cloud-free. I set up the laptop and SQM-LE and started taking a series of sky quality readings from 5:00 pm until 4:30 am the next morning. There would be about 3 hours before moonrise to get an accurate measurement of night sky quality. By 7:00 pm the SQM-LE was indicating a MPSAS value of 20.00 (5.5 NELM) and it peaked at 8:30 pm at 20.03 MPSAS (5.5 NELM). The moon had risen at 8:06 pm and as it got higher in the sky the readings continued to

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UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO

Image 7

drop. However, the limiting magnitude remained about 5.0 until after midnight when the moon was over 60 degrees up in the eastern sky. It should be noted that by placing a baggy over the meter, it was reporting a slightly darker sky than would have been reported without one. To more accurately assess sky quality, multiple readings with and without the baggy would have determined what correction factor needed to be applied to the SQM-LE’s readings. So my sky quality was not so shabby after all. It was my 60 year old eyes that were not what they use to be. I was estimating a NELM of about 4.3 while the SQM-LE calculated a value of 5.5. (see Image 5). This shows why MPSAS is the accepted gauge of sky quality – not NELM. As seen in the graph provided in Image 6, for any given MPSAS, there is a range of almost 2 magnitudes to account for the variability inherent in using “Limiting Magnitude” as an assessment of sky quality. Enter SQM-LE Reader PRO When I was working on the draft of this review, I received an e-mail from Gary Parkerson about adding a review of Knightware’s SQM Reader Pro program to that for the freeware SQM Reader and quickly said that I would. Gary contacted Phyllis Lang at Knightware

Image 8

Software and arranged for a download. For me, using SQM Reader PRO would automate the graphing of the output from the

meter and quickly show my sky’s condition. A cool front had passed through the area a few days before May 19 and my Clear Sky Clock pre-

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UNIHEDRON’S SQM-LE AND KNIGHTWARE’S SQM READER PRO dicted that sky conditions would be favorable for testing the meter with the new software. I rushed home from work, installed the software and connected the meter to the laptop. Upon opening SQM Reader PRO, I set up the IP Address of the SQM-LE, the time offset from UT and the latitude and longitude of the meter. This data is used to calculate when the Sun is up and when twilight ends. Pushing the TEST METER button confirmed that everything was set up properly. The software was configured to take a meter reading every 15 minutes whether the sun was up on not and the graph would plot 12 readings at a time. This should have been set to 48 to show the sky quality over a 12 hour time. The meter was left running all night and I shut it down at 5:15 am the next morning. Between 6:43 pm on May 19 and 5:13 am on May 20, the SQM-LE had taken 43 readings. The minimum reading (0.00 MPSAS) occurred when the Sun was up and the maximum reading occurred at 1:43 am (20.24 MPSAS or 5.7 NELM). Since several readings were taken before sunset, the Mean was only 17.17 MPSAS

50 Astronomy TECHNOLOGY TODAY

(3.1 NELM). On the night of May 19 and 20, moonrise occurred at 3:03 am, but since it was only a waning crescent, it had little effect on sky quality. However, morning twilight occurred at 4:29 am and its effect on sky quality is easily seen. The two images show the MPSAS reading graphs prepared by SQM Reader PRO for the first 12 and the last 12 readings taken (see Images 7 and 8). Using SQM Reader PRO eliminated the need to manipulate the data provided by the SQM-LE and made using the SQM-LE a whole lot easier. Things to Consider The reason I placed the SQM-LE into a baggy during my testing is because the meter is not weatherproof. It is normally mounted under an acrylic dome that is heated and with airflow below to prevent condensation. The exterior of the dome would have to be periodically cleaned of contaminants such as bird droppings. A bug screen around the meter is also necessary to prevent insects from fouling the lens on the meter. In addition, over time, the dome will weather

and cause inaccuracies in the sky quality readings provided. However, if one has a remote observatory and needs to assess sky quality before initiating a photographic session, the SQM-LE provides that service. It is not as user friendly without SQM Reader PRO, but the excellent support provided by the Unihedron team helped a non-computer geek like me to get the device working properly. Summary The SQM-LE by Unihedron (www.unihedron.com) costs $249.99 USD plus shipping and handling and SQM-LE Reader PRO (www.knightware.biz) is available as either a digital download for $40 USD or on a CD for $47.99. Teamed together, they provide an easy and effective mechanism to monitor the quality of the sky at one’s observatory either locally or remotely. Since sky quality varies over the course of a night, from night to night and throughout the year, having these tools allows one to determine sky quality over an extended period of time and to monitor the evolution of light pollution in the area.

Taurus Technologies’ Dark Sky Atlas A Tool for Finding Your Next Dark-Sky Observing Site The main screen of the Dark Sky Atlas showing data from one of the author's favorite local observing sites discovered using that same atlas.

By Gary Parkerson

Although my duties with this magazine keep me more than enough occupied with astro stuff, like many of you, I still daydream about additions and modifications to my personal collection of scopes and such, and as my vision diminishes with age, I too try to compensate with more capable equipment. But, since working with Roger Blake of Taurus Technologies on articles covering his Virtual Observer Project, I find myself spending far more time daydreaming of darker observing sites than of ever more aperture. I suppose I was already aware to some degree of the relative importance of sky darkness versus aperture. I’ve been fortunate enough to observe from some of the darkest sites in the country where, on

more than one occasion, my old 10-inch Newtonian produced views that an 18inch Dob could not match from my lightpollution impacted backyard. But I was clueless to the full impact of what I once thought were negligible increases in darkness until awakened by Roger’s research. The truth of Roger's findings was dramatically reinforced by my observations with that same 10-inch Newt when I spent one night viewing under skies for which a Unihedron Sky Quality Meter (SQM) reported a magnitude per square arcsecond (MPSAS) of 20.76, roughly equivalent to a Naked Eye Limiting Magnitude (NELM) of 5.98, and the next under skies with an SQM measured MPSAS of 21.51 (NELM of 6.39), care-

fully recording observations of specific objects from both locations. To summarize just one example, what was from the first site a ho-hum view of a few galaxy smudges in the Virgo Cluster was at the second site transformed into an eyepiece field filled edge to edge with numerous galaxy forms of surprisingly greater detail – far more detail than I was prepared to credit to a mere 0.4 limiting magnitude increase. The result was a new interest in searching for similar increases in sky darkness at sites even closer to home! But how to go about that? Enter Roger Blake’s Dark Sky Atlas, the software program that combines high-resolution light pollution maps with an interface that Astronomy TECHNOLOGY TODAY

TAURUS TECHNOLOGIES’ DARK SKY ATLAS is so easy to use, even I was able quickly master its various functions. The Dark Sky Atlas (DSA) presents most of the tools I needed to conduct an effective search on its well-organized main page (see accompanying image), which is divided into three main sections. The main page presents a 190 by 134 mile map section that displays major geographic details, including primary roads and cities, overlaid by a high-resolution, color-coded graphic indicating areas of relative sky darkness. After using the DSA for many months now, I’ve come to agree that 190 by 134 miles provides the optimum scale for most searches. Below the map section is a colorcoded legend that indicates the ranges of Limiting Visual Magnitude (LVM) from 5.0 to 7.0 and Magnitudes Per Square Arcsecond (designated “MSA” by the Dark Sky Atlas) from 18 to 22. This legend includes a clickable link at each whole and half MPSAS mark, denoted by the image of an eyepiece. Click on one and it

Astronomy TECHNOLOGY TODAY

opens an image of M51 that is representative of what many will see of that highlight object when viewed through a typical telescope from a location of corresponding relative sky darkness. Navigating the Main Page Map To the left of the map section appear functional sections designated “Navigation” and “Cross-Hair Results.” The Navigation section lists six methods for using the map. The first entry instructs the user to simply “click” anywhere on the map section to position a cross-hair symbol at a specific point, and the Cross-Hair Results section provides critical data for any map point identified by the cross-hair symbol. The second navigation method entry provides four clickable compass points – click on any to move the area displayed by the map in that direction. I found myself using this method more than any other for quickly positioning the map to and

scanning a desired region. The third navigation method provides for direct entry of numeric longitude and latitude data to position the cross-hair symbol at the point of intersection of those exact coordinates on the main map. The next navigation method provides a clickable link labeled “Zoom Out” that opens a much wider map section: a 3 by 3 array of 9 of the standard 190 by 134 mile map sections. Click on any of the 8 edge maps to move that map section to the center position or click on the center map section or click the “Close” button to return to a standard single map section view of that center map section. I‘ve only recently gotten in the habit of using this method of navigating the overall map, but am quickly finding it even easier than using the four clickable compass points in the second navigation method. The fifth navigation method provides another clickable link designated “Find a City.” Clicking it opens a list of the 50 states and clicking on any state in that list

TAURUS TECHNOLOGIES’ DARK SKY ATLAS opens another of cities within that state. Clicking on a city opens the main page map section containing that city. The final method listed in the Navigation section provides a clickable link to a list of 34 major annual star parties. Clicking the Okie-Tex Star Party entry centers the cross-hair symbol at the site of that event and...wow, it’s much darker there than I realized! I’ll have to make a point to attend this year. Data for the Cross-Hair Coordinates The Cross-Hair Results section is located below the Navigation tools to the left of the main page map section and identifies the latitude and longitude for the specific map position identified by the cross-hair symbol. That data is followed by year 2000 light pollution values at sea level in MSA and LVM for that position, its altitude measured in feet, and then maximum, annual average and minimum MSA and LVM values recorded for the position during 2008. These later values are altitude adjusted and 95 percent of actual measurements for any given set of coordinates are expected to fall between the maximum and minimum values reported for those coordinates by the DSA. The annual average value represents the expected average of many actual measurements taken over the course of a year. The light pollution values are calculated to represent sky brightness as impacted by both natural and man-made

factors, under dark, clear sky conditions – those with no moon and recorded after and before astronomical twilight, sans clouds, haze and fog within 50 miles of the reported position. I‘ve now had the chance to compare measurements taken from a number of locations using a Unihedron SQM with the values reported for those locations by the DSA and have confirmed that the atlas is surprisingly accurate. Although my actual measurements represent an admittedly small sample of locations and nights, I am nevertheless confident in the useful accuracy of the atlas’ data. Below the Cross-Hair Results section is another clickable tab entitled “The Sky Dome.” This useful tool opens a screen that displays the variations in sky brightness an observer at the cross-hair location would see as he or she looks 45 degrees away from the zenith, to the north, south, east and west. Because the main map graphic displays year 2000 data and the Sky Dome data is current, the later may appear to contradict the map in highgrowth municipal areas. I found the Sky Dome data to accord well though since my searches generally emphasized relatively remote, dark regions. The Sky Dome data represents changes in light pollution relative to that at zenith and is presented as percentages of change. For example, the Sky Dome data for my backyard location accurately represents the reality that skies are 0.88 and 0.82 MSA darker 45 degrees north and west from

zenith respectively, while 0.58 and 0.30 MSA brighter 45 degrees toward the east and south. Using the Dark Sky Atlas As I mentioned earlier, my first impulse was to use the DSA to identify darker potential observing sites convenient to my home location. Working with the atlas and Google Earth, I quickly identified an abandoned munitions dump that had been integrated into a wildlife preserve and that is less than a 30-minute drive from my home. The location offers a number of excellent observing sites all accessible by paved drives and secluded from outdoor lighting and traffic. The best news though is that the location boasts an annual average MSA of 21.25, almost a whole MSA unit darker than is offered above my backyard observatory. I now spend a couple of nights each month enjoying the relative darkness of this nearby observing site and simply would not have found it without aid of the DSA. When planning a recent trip to visit my brother who lives in central Missouri, I used the DSA in combination with Google Earth to identify several potential dark-sky sites within the protected borders of a state park less than an hour from his home. During another recent trip to Colorado, Utah, Nevada and New Mexico, I was able to use the DSA together with real-time GPS data from my Blackberry to locate a number roadside dark sites during full daylight. By the way, if you’re ever in the Four-Corners area, consider

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TAURUS TECHNOLOGIES’ DARK SKY ATLAS scheduling an evening in the Valley of the Gods loop. It’s as dark as any remote site I’ve had the pleasure of visiting! While admitting to daydreams I may as well confess another: eventual retirement to a truly dark-sky, high-desert area of the country (and one with much lower humidity than we endure here in Louisiana). The DSA has made my increasingly serious search for a retirement home much easier as well and I’ve now used it to identify and evaluated several available properties in areas that I simply would not have thought to consider but for the atlas. I’m having almost as much fun using the DSA to identify potential locations and then “touring” them by air via Google Earth's 3-D images as I anticipate having viewing the heavens with my favorite scope from one of those same future dark-sky home sites. Version 2.2 Enhancements I mentioned using the DSA in com-

Astronomy TECHNOLOGY TODAY

bination with Google Earth and the two programs do indeed compliment each other very well – so much so that Roger has added links to Google street and satellite maps in Version 2.2 for easier coordination of those resources. The upgrade to Version 2.2 is free to current users of the DSA and the link to Google's map data is positioned just above The Sky Dome link in the lower left corner of the main page screen. Other Dark Sky Mapping Options While on the subject of Google Earth and other Google map programs, I should note that similar color-graphic sky-brightness overlays are available for use with those Google resources. I have loaded one such Google Earth overlay on my home computer and have used it enough to conclude that I simply prefer the more taskspecific functionality of the Taurus Technologies DSA.

Conclusion I had no trouble loading a previous version of the DSA in systems using both Windows XP and Vista, nor in subsequently updating them to Version 2.2. For those who question whether $35 is too much to pay for software that they may anticipate only using a few times, I can only offer that I would have gladly paid much more to locate that former munitions dump I now consider my observing home away from home. But, if you’re anything like me, you’ll find yourself consulting the Dark Sky Atlas whenever you plan any trip within the confines of the U.S. Indeed, if there’s a significant negative to this tool, it is only that it is currently limited to data for the area of the mainland United States. An audio/video tour of the Dark Sky Atlas is available for download from www.taurus-tech.com and is a great way to see if the program might prove as valuable to you as it has to me.

The Backpacking Astronomer An Easy-To-Carry, Multipurpose Observing System for Hikers By Erik Wilcox

As an avid hiker who often finds himself in the middle of nowhere as night approaches, I always make sure to take along the essentials; food, water, first-aid kit, a hand-held GPS unit, and of course, a scope. With all the aforementioned objects (as well as many other I’ve left out), weight becomes a big issue. So, as much as I would enjoy looking through a large-aperture telescope at some of the dark, isolated places I hike to, it’s often not practical to lug extra weight along. I’ve researched, used, and owned many small telescopes, binoculars, monoculars, and spotting scopes, many of which I’ve attempted to take on hiking trips, and what I’ve often found is that the mount itself can be more cumbersome than the telescope optical tube assembly (OTA). Any type of equatorial mount is generally out of the question because of relative weight and bulk. I found that even the svelte Orion Mini-EQ mount (essentially an EQ-1 mount with miniature screw-on legs to replace the standard tripod legs) combined with its popular Short Tube 80-mm refractor is still too much gear for most hiking trips. And alt-azimuth mounts designed for astronomy are often too heavy and bulky to be considered

Right: The Nikon spotter mounted on Trek-Tech's TrekPod

truly “backpackable.” For a while, I tried several camera tripods combined with various small refractors, but even with those, the mounts were often overtaxed and too shaky at any magnification. It seemed that what I needed was something that could perform double duty, so no extra weight or bulk would be added to what I would already be carrying. I finally found that in a product called the TrekPod (which I described briefly in an earlier issue of ATT). What looks and performs like a high-quality hiking staff quickly turns into an adjustable tripod capable of carrying my Nikon 65-mm spotter, small to medium binoculars, or a DSLR camera. The TrekPod is rated at 9 pounds of carrying capacity, and, while that seems a bit high to me, it does hold my 2.5-pound spotter nice and steady. Even at 48X, I can easily keep objects in the field of view, thanks to the smooth, adjustable motion of the TrekPod's ball head. The head even features a “cutout,” so that it is possible to view the zenith, and as a hiking staff, it is solid and lightweight, and doesn’t bend or “give” when putting full body weight on it like many other lesser hiking staffs do. What I’ve personally found most limiting

about the TrekPod is not that it gets “shaky” with heavier scopes, but that it can get too top heavy with such instruments, which could lead to it and the scope accidentally tipping over. Unlike backyard observing, doing so while hiking often means observing in poor conditions, with rocky, unlevel ground, high winds, etc. So this is a real concern and I sometimes place my backpack on top of two of the legs just to “weigh the mount down” a bit. Also, because the TrekPod extends to just over 62 inches, kneeling or bending over becomes necessary when attempting to view the zenith. But in my opinion, these are small prices to pay for the convenience of having a built-in tripod on the hiking staff that is necessary to hiking anyway. For more info about the TrekPod, as well Astronomy TECHNOLOGY TODAY

THE BACKPACKING ASTRONOMER wonder why one would choose a spotting scope instead of a traditional refractor. For me, there were several reasons. Most of all, a spotting scope is convenient; no need to change eyepieces, etc. It’s also lightweight and compact, with no bulky tube rings, finderscope, large focus knobs, and such. But another big reason is that many spotters are waterproof or waterresistant, which often Closeup of the TrekPod ball-head mount. comes in handy on hiking trips when the as Trek-Tech's newer, even lighter-weight carweather can turn ugly in an instant. Some spotbon-fiber hiking staffs/tripods, please see their ters are also nitrogen filled, which eliminates website at www.trek-tech.com. fogging, and some, like the Pentax ED spotRegarding the optical tube, some might ters, can use standard 2-inch eyepieces and fil-

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56 Astronomy TECHNOLOGY TODAY

ters, if desired. All in all, when everything is factored in, it’s my opinion that spotters are much more versatile for hiking than standard telescopes, especially if the user wishes to also use it for daylight observing. While viewing astronomical objects is what I do most often, it is nice to be able to quickly observe a bird or animal from a distance during daylight as well. Another piece of gear that I consider standard equipment for hiking trips is a small monocular. For quick views, it’s much faster than pulling the spotting scope out of the backpack, and it too can be mounted on the TrekPod if desired. What I often do is use the TrekPod in its monopod form (without the three tripod legs extended) and mount the monocular with one of the included supermagnet TrekPod MagMounts (which I use with the spotter as well; the TrekPod also features a safety clip so that attachment of the scope doesn't rely on the magnetic connection alone). I looked at and compared many different monoculars in various price ranges before choosing the somewhat obscure Carson XV 7x32 unit. It has a built-in threaded 1/4-20 mounting hole, rubberized “armor” covering, and, for the price (around $75), has excellent multi-coated wide-field optics. It also has a dual-focusing mechanism, which in addition to reaching infinity, allows for an extremely close focus; down to 18 inches! I’ve found this useful on more than one occasion for an upclose look at plants, flowers, bugs, etc. And believe it or not, it works nicely for casual views of the moon and stars, with very little edge aberration (just a touch of field curvature in the outer third of the field of view – not seen in daylight) and crisp, bright views despite its limited aperture and physical size. Because it can be clipped on a belt or pocket, it gets a lot of use on the trail for bringing numerous objects closer, and I find its 7x magnification to be just the right magnification for hand-held use. Many hikers use binoculars for birding and astronomy, but I’ve personally found that the additional weight compared to a monocular doesn’t outweigh (pun intended) the slightly better views provided by using both eyes. Ad-

THE BACKPACKING ASTRONOMER ditionally, binoculars can get banged around in a backpack and sometimes require recollimation. While most binoculars can be user collimated, it’s not something I wish to do on long hikes. With the array of new products using cutting-edge technology, it may only be a matter of time before some company releases a truly multi-purpose optical device suitable for everything from viewing close-up weather erosion on a lava rock to seeing dust lanes in a distant 14th magnitude galaxy, but until then, different objects and observing conditions often require different instruments. For the multiple applications, including astronomy, presented while hiking, birding, and camping, I think a spotter and little monocular, combined with the TrekPod, cover typical applications reasonably well. And finally, I must apologize, as this article focuses less specifically on astronomy than most others I’ve written. But as someone who loves the outdoors as a whole and knows that most other astronomers do as well, I hope you’ll forgive me for straying a bit this issue.

Astronomy TECHNOLOGY TODAY

The Spike-a Focusing Mask A Masterfully Executed Bahtinov Mask By Craig Stark

Astrophotographers can be a picky bunch: We expect to be able to hold a position in the sky counteracting the earth's rotation to within an arcsecond, or even a small fraction of an arcsecond. To give you a better idea of what that means, an arcsecond isn’t even as big as the angle that’s formed when you put two meter sticks atop each other and put a piece of paper between them at one end. In fact, that’s about 25 arcseconds. We also expect to hit focus dead-on. While visual observers have eyes that can focus and accommodate for imperfect focus, CCD cameras don’t have this luxury. Run at f/4 and if you can’t get the focus set to within 0.035 mm, you’re inducing more

that 1/4 wave of error. That nice highStrehl telescope means nothing if your focus isn’t spot-on. To give you an idea of that degree of precision, the thickness of a piece of paper is 0.097 mm. The focus tolerance then is under half the thickness of a piece of paper (at f/7 the tolerance is about the thickness of that paper). As I said, we're a picky bunch. There are a lot of tools available that try to help us achieve this precision and hit solid focus, but none has taken the community by storm as much as the Bahtinov mask. The Bahtinov mask is related to the Hartmann mask that has been around for some time. Both are devices that you place over the front of your telescope. These

masks cause a diffraction pattern that can be used to fine-tune focus. But, the Hartmann, while not quite a Model T by comparison, is not in the same league as the Bahtinov. Pavel Bahtinov, an amateur astrophotographer, developed the idea and math behind the mask and this idea was taken up by the community at large first with a vigorous discussion on the popular astronomy forum, Cloudy Nights (www.cloudynights.com). It was fun to watch the community work together to truly build the proverbial better mousetrap and after a number of masks were made using whatever folks had on hand (cardboard, clear plexiglass with tape making the diffraction

Astronomy TECHNOLOGY TODAY

THE SPIKE-A FOCUSING MASK viewfinder or LCD screen, stop reading now and order a mask. You’ll thank me.

Image 1: Mask mounted on a Celestron CPC 1100 XLT scope. Note the clean machining, anodized finish, and nice non-marring screws used to securely anchor the mask to the scope.

pattern, etc.), several had the bright idea that it sure would be nice if someone made them commercially. Enter Jerry Hailey and John Wunderlin of Spike-a (www.spikea.com). Now, I’ve tried a lot of focusing tools and I’ve even written computer software to help you reach focus. I can say without reservation that the Bahtinov mask is one of the easiest (if not the easiest!) methods, to focus your scope. I’ve also made a number of Bahtinov masks myself and I’ve seen a few commercial offerings. I can also say

without reservation that the Spike-a mask is the best-made version I’ve seen. While about $80 for an 8-inch mask is a lot more expensive than a piece of cardboard and a razor blade, the Spike-a version is a lot more sturdy and a heck of a lot classier than my home made attempts. If you’re using a dedicated CCD to image with (and are therefore using image capture software that probably has a focus routine), think long and hard about using a mask, as it may make your life a good bit easier. If you’re using a DSLR and trying to focus with its

The Spike-A Mask The Spike-A mask is made out of nicely machined and anodized aluminum (Image 1). The main portion of the mask has a series of slits cut into it that produce the diffraction pattern used during focusing. This is considerably stronger than say, the thin cardboard box that used to hold a pack of manilla folders (ahem!). One of the issues facing the homebuilder after the mask has been, say cut out of said cardboard, is how you attach this to the front of the scope. Sure, there are homebrew solutions and a number of people out there have done wonderful jobs. I tend towards the quick-and-dirty approach and the “spring” I made out of folds of said cardboard worked...mostly. In the Spike-a version, three tabs of the aluminum are bent over and nylon screws are inserted through threaded holes. This way, it can securely attach to the front of the scope (foam pads protect your scope). Did I mention this looked more professional and was a lot sturdier? Using the Mask The mask is easy to use. Simply aim your scope at a fairly bright star and put the mask over the front of the scope. What you’ll see with the mask in place is the star with Vs coming off of two sides and a line that’s either on one side of the V or in the middle of the V (see Image 2). As you turn

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THE SPIKE-A FOCUSING MASK the focus knob, the line will either move towards the center of the V or away from it. Get the line centered and you’re in perfect focus. That’s it. Image 2 shows a demonstration of this. In each panel, I’m showing the star as viewed with (top) and without (bottom) the mask in place. Visually, it’d be tough to know exactly where focus was if all one had were the star’s raw image (images taken with a Canon Rebel XSi and a Celestron CPC 1100 XLT). Is the first one in focus or not? With the mask in place, it’s easy to see that we’re out of focus. As we move in a bit more (upperright) and then more (lowerleft), the line gets closer to the middle of the V. Looking just at the star in the lower-left, you might think you’re in focus. You’d be wrong though as the mask shows the line is near the middle of the V, but not quite there. Touch the Image 2 - Figure 2: Each panel shows the image of a star both with (top) and without (bottom) the mask focus knob a bit more and attached. Position of the focuser moves from frame to frame. Away from focus, the horizontal diffraction line you’re spot-on and in focus. is not centered on the V-shaped diffraction lines on either side of the star. In focus (lower-right), the line is perfectly centered on the V. Which side of the V the line is on tells you which side of focus you're on. Done. Can you focus without done this myself and have an entry in you’re just close. With the mask, there’s no it? Sure. In particular, if you’ve got a focus my blog showing how this is done room for doubt. While I rarely actually use tool that’s monitoring the star’s FWHM (http://www.stark-labs.com/blog/files/Nebmy DSLR for astrophotography, focusing (Full Width Half Maximum) or HFR Bahtinov.php). This can be particularly it with the Spike-a mask and Live View was (Half Flux Radius), you can often hit focus helpful if you’re trying to focus with a nareasier than any other focusing setup I’ve without much hassle. I’ve not clocked myrow-band filter in place. You can often hone used. By the time I was done with this self, but I’d not be at all surprised if the in on focus with fewer iterations with the setup, I’d barely have gotten started with mask isn’t a bit faster and it’s certainly easmask. my normal setup (which I already consider ier to know when you’re there as you have The Spike-a mask works very well in simple and efficient). an absolute reading (the line being in the these situations. But where it truly shines middle of the V) and aren’t relying on it and becomes not just a great tool, but inSummary being better or worse than other focus dispensable, is when you’re trying to focus In summary, the Spike-A mask does positions (what’s my best possible FWHM and only using your DSLR’s LCD screen. exactly what it’s designed to do and does it tonight?). There’s also nothing stopping Even with Canon’s Live View streaming very well. Put it on the front of your scope you from using the mask while your images, it’s still often tough to know and you’ll be able to find focus quickly and software loops images of the stars. I’ve whether you’re really there or whether accurately. It’s easy enough that my five Astronomy TECHNOLOGY TODAY

THE SPIKE-A FOCUSING MASK year-old could do it. Heck, my three yearold probably could too. When the Spike-a masks first came out, I didn’t know how well they’d work and Spike-a’s prices were a good bit higher than they are now. So, I went the cardboard and razor approach. This worked well until the mask got mangled in transport. Now, having to do it over again (I don’t image much with the CPC 1100 XLT these days), I’m faced with the choice of not using the mask, making another one out of cardboard, or picking up one from Spike-a or one of the other ven-

62 Astronomy TECHNOLOGY TODAY

dors selling masks. As I’m in this hobby longer and longer and as my free time seems to always get shorter and shorter, I find myself gravitating towards (or just hanging onto) gear that just plain works. Heaven knows, my old Takahashi EM-10 mount isn’t fancy (it’s go-to system requires an attached computer, is based on a one-star alignment, and has slews that are honestly quite pokey) and its size limits my OTA load considerably. But, each time I set it up, it just plain works. Polar alignment is a snap and its error small and easily removed with

guiding. I never have to think about it or worry about it because each night, it just plain works. As a result, it’s stayed as my mount despite the seemingly perpetual revolving door of gear. The Spike-a mask is a lot like this. It’s well-built and it just plain works. Toss it in the car with the rest of the gear and I know I won’t be fighting focus issues and I know I won’t be staring at a mangled focusing mask on the other end. I also know that in a year (or in 10), the mask will still be around performing exactly as it’s doing now.

The Cambridge Double Star Atlas By James R. Dire, Ph.D.

I haven’t been this excited over the release of a print-version star atlas since Wil Tirion’s Sky Atlas 2000 in 1981. So when Cambridge University Press announced they were ready to ship their new Double Star Atlas in April 2009, I must have placed the very first order on their web site. This nicely done spiral-bound book is the joint work of James Mullaney, former assistant editor at Sky and Telescope magazine and renowned astronomy author, and Wil Tirion, the best-known living stellar cartographer on this side of Alpha Centauri. While a senior in college in Kansas City in 1981, I bought my first quality telescope, a Criterion RV-6 (6-inch f/8) Newtonian reflector. Living in a large, light-polluted metropolitan area, searching for nebulae and galaxies would have been very difficult. Viewing double stars seemed to be the best way to kick-off my observational career. I didn’t need really dark skies, and found binary star systems quite fascinating. Tirion’s first work was quite useful in helping me steer my Newtonian towards these celestial jewels. Astronomy TECHNOLOGY TODAY

THE CAMBRIDGE DOUBLE STAR ATLAS Atlas

Epoch

Limiting mag.

No. of charts

Stars

Deep space objects

Norton Star Atlas 20th Ed.

2000.0

6.5

8,800

600

Cambridge Double Star Atlas

2000.0

7.5

25,000

900

Sly Atlas 2000.0 Deluxe Ed.

2000.0

8.5

81,000

2,700

Table 1

However, Sky Atlas 2000 did not contain information on the components’ individual brightness and separation, resulting in my sighting countless binary stars that I could not resolve. The Cambridge Double Star Atlas is an excellent composition containing all that is needed to explore double stars. It starts with an 11-page introduction to viewing double stars, followed by a table of 133 showpiece double and multiple stars that can be spied in telescopes with apertures from 2 to 14 inches. The atlas contains 30 plates, 8.5 by 11 inches in size, covering the entire celestial sphere. Nearly 2,400 double and multiple stars are plotted on the plates, each labeled with the discov-

erer, catalog and/or observatory index number. The double stars plotted have a limiting combined visual magnitude of 7.5 with no double stars identified with components fainter than 10th magnitude. Pairs separated by more than 3 arcminutes are plotted as separate stars. Each plate covers between 1,200 and 1,400 square degrees of the sky. The background is white with solid black circles for stars; as is typical, the larger circles indicate brighter stars. Double and multiple stars have a horizontal line through the circle while variable stars have a concentric ring around a solid circle. Star clusters are yellow, nebulae are yellow-green and galaxies are red. The Milky Way is indi-

cated by two shades of purple, the darker shade denoting the inner Milky Way. All labels are black except double and multiple star labels, which are green. A legend appears at the top of every page to help identify object classes and estimate the brightness of all plotted stars to within a half magnitude. The atlas has three appendices; the largest and most useful is a table listing all of the double stars plotted in the atlas in order of increasing right ascension. Each line also contains the stars’ constellation, designation as labeled on the plates, and the components’ magnitudes and separation in arcseconds. The strength of this atlas is that it contains double and multi-

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THE CAMBRIDGE DOUBLE STAR ATLAS ple stars plotted on plates and catalog information all within one bound book. The catalog data and plates go hand in hand in picking observing targets and it is a simple matter to flip back and forth. The only thing that could have made this process easier is if the Appendix C table listed the stars by constellation or plate number instead of strictly by right ascension. The Cambridge Double Star Atlas can be used for more than just double star hunting. As for the number of stars plotted, it falls in between the Norton Star Atlas and the Sky Atlas 2000.0 Deluxe Edition. However, the look is more like that of the Sky Atlas Deluxe Edition due to the similar color scheme. The Norton Star Atlas only uses black on white for all objects and labels, with one shade of green for the Milky Way. Table 1 compares the three atlases. Of the three star atlases compared in Table 1, I like the look, size and feel of the Cambridge Double Star Atlas the best. The

spiral bound book is just large enough to make the plates easy to read, whether under white or red light, but not so large as to monopolize desk space. Plus, each page has a thin coating that resists condensation. The double star designations contained on the plates don’t excessively clutter the charts when using them for general observing. Finally, I’ll offer a few words comparing the Cambridge Atlas with electronic star atlases. Double star information can be found on many popular planetarium programs such as Starry Night, The Sky and Voyager. I use Voyager (by Carina Software) extensively for telescope control in my observatory (www.wildwoodpines.org). Double stars labels can be toggled on and off with one mouse click and settings can be adjusted to only display double star labels for certain limiting magnitudes, magnitude differences, and component separations. The number of double stars that can be displayed grossly exceeds those contained on a print star atlas.

So why would anyone ever need a bound paper double star atlas? Electronic star charts are great in observatories with computers and AC electric outlets. But when I am hauling my big Dob and fourstep ladder halfway across the state to a remote dark site for an all night visual observing session, its just easier keeping a light-weight paper atlas and small red flashlight (with a spare set of batteries) on the top tray of the ladder than a laptop computer. The computer battery won’t last all night and it’s not likely I’ll have anywhere in the middle of nowhere to plug it into. The Cambridge Double Star Atlas’ limiting visual magnitude for faint components is just perfect for visual binary star hunting!

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A PVC Secondary Mount on a Wire Spider

My ATM Solution For Suspending a Secondary

By David Merritt

When I began designing Sauron's Other Eye, my 16-inch reflector, it wasnâ&#x20AC;&#x2122;t clear to me how I was going to mount the secondary mirror. I purchased the optics, put together a preliminary design, and started working on the mirror cell without facing the dilemma. Not until I was ready to put together the upper tube assembly did I force myself to get specific. My only initial vision was to have a three-vane spider. I vaguely knew that I wanted to minimize diffraction effects and vibration, but mostly I wanted to avoid the difficulties that I'd had with the secondary on my home-made 10-inch reflector. That secondary holder consisted of a 4-vane spider supporting a central threaded rod that held a wooden wedge with three adjustment screws. It was a modified commercial product from the 1970s and I'd never been quite comfortable with its modifications. Among the minor annoyances, it was hard to reach one of the adjustment screws because the spider vane blocked the screwdriver, and there was a fairly large lateral motion of the secondary mirror whenever I attempted to adjust its tilt. Studying designs that I found offered commercially, as well as other home-built versions, gave me some inspiration, but

none of them really satisfied me. Most commercial secondary mounts still retain that cantilever between the adjustment and the mirror face, so that adjusting the tilt angle requires simultaneously adjusting the lateral position. So, when I began to visualize what I wanted, I came up with the following requireSauron's Other Eye, built around a 16-inch f/4.5 Bob Royce mirror ments: (1) Minime unmercifully. And, since the commermize the distance between the tilt axis and cial options I couldn't afford didn't seem the mirror face; (2) Allow for easy adjustto give me what I wanted anyway, I was ment without tools; (3) Once adjusted, reable to decide to go home-made without main positionally stable; (4) Minimize guilt. diffraction effects; (5) Minimize vibrations I considered several designs using and wind resistance; (6) Be relatively lightwooden blocks or metal plates, but all of weight, and of readily available materials; them looked unwieldy to use or difficult to and (7) Low cost. fabricate. I was about to give into frustraI'd already spent most of my budget tion when I took a break to replace a leaky on the optics and structural materials (it's PVC connection in our irrigation system. I mostly a fiberglass/foam composite) and remembered how easy it is to cut PVC my inner cheapskate was beginning to nag Astronomy TECHNOLOGY TODAY

A PVC SECONDARY MOUNT ON A WIRE SPIDER

Image 1 Cross-sectional schematic view of the secondary holder.

pipe, and how it's relatively lightweight. As a material, it's not hugely stiff or strong, but in short lengths and small loads, it seemed like it might be the perfect solution. I began to design from a different perspective. The basic concept is a hollow tube penetrated by three radial bolts spaced 120 degrees apart. The bolts push against a shaft running longitudinally through the tube, supported at one end by a tightly fitting rubber grommet. This grommet is the pivot point of the shaft, which can be tilted in any direction by screwing the radial bolts in or out. The grommet also dampens vibrations and grips firmly enough to keep the bolt from pulling outward under the weight of the mirror (Image 1).

68 Astronomy TECHNOLOGY TODAY

Image 2 The PVC parts prior to cutting and fitting. Not all the pieces shown were actually used â&#x20AC;&#x201C; I dispensed with the cap nuts on the ends of the adjustment rods and used a hex nut at the proper location on the threaded adjustment shaft.

I used three different sizes of PVC pipe. The largest is 2-inch (PVC pipe is rated by its inside diameter, which is always slightly larger than nominal) cut at a 45degree angle to hold the 3.1-inch secondary mirror. The support for the spider and the adjustment knobs is a 1.25-inch size, and a short piece of 1/2-inch pipe holds the rubber grommet. The narrowed mirror-side portion of the tube allowed me to insert the pivot point much closer to the back of the secondary mirror to limit lateral motion during adjustment. I used a 1-inch by 1/2inch reducer bushing to connect the small grommet holder to the adjustment tube. I had to build up the male end of the bushing with vinyl tape to get a snug fit, and made it permanent with epoxy. Epoxy was

the logical choice for cement at the time, since I was already using it for the fiberglass layups. Adding milled glass fibers to the mix before it hardens makes the epoxy extremely strong â&#x20AC;&#x201C; probably more so than I actually needed. For a general adaption of this design, something like JB-Weld might work just as well. I'd recommend avoiding the instant epoxy putties, however, as they tend to be relatively weak and brittle. The adjustment shaft is a 5/16-inch machine bolt 3 inches in length. I anchored it to 3/8-inch thick plywood cut into a circular shape to fit inside the large pipe. Again, I used epoxy to attach the plywood into position (Image 2). I drilled out the holes for the 8/32inch threaded rod pieces that comprise

A PVC SECONDARY MOUNT ON A WIRE SPIDER

Image 3 PVC subassemblies

Image 6 Adjusting the tension on the wire. One wrench loosens the lock nut and the other rotates the rod.

Image 4 PVC subassemblies

Image 7 Hand-adjusting the secondary assembly.

Image 5 Anchoring the wire spider with threaded bolts in the upper tube ring.

Image 8 Adjusting the secondary mirror tilt using the knobs. Astronomy TECHNOLOGY TODAY

A PVC SECONDARY MOUNT ON A WIRE SPIDER the radial adjustment screws, and made very shallow enlargements in which to embed their hex nuts. As always, I used fiber-fortified epoxy to glue both the hex nuts and the knurled adjustment knobs into place. Once the epoxy set, I cut everything to the proper length and angle, glued the grommet to the narrow end of the adjustment tube, and embedded the bolt into the remains of the plywood disk. The disk was placed so that cutting the mirror holder at 45 degrees removed slightly less than half the disk, allowing just enough room to keep it from contacting the back of the mirror (Images 3 and 4). Up to this point I had concentrated on mounting and adjusting the secondary mirror, but still hadn't decided what to use for a spider. I toyed with the ideas of curved vanes, of flat vanes, of triangular raised vanes from a single UTA ring, even of vanes doubling as light baffles, but I couldn't get anything that was either in my price range or within my skill set. Finally, inspired by Mel Bartels’ and some other websites, I settled on the idea of a wire spider. Once that decision was out of the way, things progressed quickly. My design uses eye-screws on the center tube, and threaded rods extending above and below the upper tube ring. Tightening uses the “guitar-tuning” model – the wires are wrapped around the support shafts in such a way that they can be tightened or loosened by turning the shafts. Knowing that there would be sig-

70 Astronomy TECHNOLOGY TODAY

nificant tension in the wire support, I embedded wooden blocks in the ring to strengthen the area where the bolts pass through. It wasn't pretty at first! I have a friend who tunes pianos and he had some spare piano wire to offer, but it was too thick and so stiff that I couldn't thread it through the eye screws. Determined to use thinner wire and to minimize diffraction as much as possible, I visited a guitar store and bought several 9-gauge strings (0.009 inch in thickness). Things looked good until one of the strings broke while tightening. A second trip to the guitar store netted me 13-gauge strings and an unrequested discount from a sympathetic proprietor who thought my usage was novel enough to be worthy. Those didn't break, but they generated enough stress on the eye screws to require a larger size of those. Guitar strings do stretch, and I had to adjust the tension several times over the next few weeks. Since they stabilized though, they've held up very well. I mounted the strings on 5/16-inch threaded rods that pass through the upper ring and extend 2 inches on either side. The wire wraps around a short piece 0.75inch thin-walled aluminum tubing left over from the trusses; a small hole drilled in one side accepts the wire end. Cap nuts, washers, and hex nuts keep the wire constrained and allow for tension adjustments (Image 5). Adjusting the spider violates my “no tools” philosophy for setting up this

A PVC SECONDARY MOUNT ON A WIRE SPIDER scope, but the adjustments are minor, and once the wire is stabilized, rarely need to be redone. Two wrenches are required: one to loosen the appropriate hex nut on the UTA ring (which locks the rod and prevents turning) and the other to simultaneously turn one of the end nuts to either loosen or tighten the wire. The process is much like collimation – not intuitive at first, but eventually you get a feel for it (Image 6). Each wire crosses itself as it loops through the eye-screws on the secondary mount and ends at the opposite end of the same mounting post. I considered a system more like that used by Mel Bartels and others, where the wires offset by 120 degrees to the next post. Such a system is rotationally stiffer, but less easily adjusted. I've found no disadvantages to my simpler scheme; even though I can rotate my secondary assembly easily by at least 10 degrees, in practice there's no outside rotational tendency to begin with, and I don't notice any vibration problems resulting from it. The advantage of the straightforward string plan is that I have more freedom of adjustments to use. I can tilt the entire assembly with a twist of the wrist if I want to fine tune the lateral position of the secondary mirror, and the wire slips through the eye holes easily enough to go where I want it too, yet it's held tightly enough to stay where I put it, with no drift (Image 7). And of course, I can adjust the secondary mirror tilt the old-fashioned

way, using actual adjustment knobs! (Image 8). This is what I designed the system for, and it does what it should – tilting the mirror with a minimum of lateral displacement. Between the different methods of adjustment, I can get the mirror centered in a standard Tectron sight tube to prepare for primary collimation. Images 7 and 8 show a couple of other things. First, the extra holes in the structure caused by some trialand-error drilling in places that didn't work, and second, a piece of twine siliconed on one end to the mirror back and on the other to the inside of the mirror mount. This is a direct imitation of Erik Wilcox's safety device to prevent the complete loss of primary and secondary in case the cement on the edge of the mount tube ever fails to hold. In use, I'm very pleased with this system. The six diffraction spikes are very faint – much less than I expected. On a relatively bright star like Polaris, they are almost in-

visible. The secondary has plenty of stiffness and no visible drift at different altitudes. Any breeze strong enough to cause vibration in the secondary also causes more from the light shield, so the scope's overall wind threshold is reached well before that of the secondary. The final result is a device that is relatively original, easy and fun to build, inexpensive, adjustable, and performs well. I'm pleased!

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ASTRO TIPS tips, tricks and novel solutions

Upgrading Those Tiny Telrad Alignment Knobs A Cheap, Easy and Simple Solution to a Common Problem By Steve Sands I am an avid fan of Telrad zero-power finders for several reasons. Primarily though, I find their three-ringed illuminated target (circles of 0.5, 2 & 4 degrees) to be particularly useful, especially in light of the myriad of after-market products that cater to the “Telrad Crowd” which greatly enhance their use. These include pulser modules, dew shields, risers for convenient viewing, and excellent sky charts for star hopping, to name just a few. Some folks object to the size and weight of the Telrad finders, but I think that the pros far outweigh the cons. Steve Kufeld really got this one right! However, there is one particular “feature” of the Telrad that I have always found to be quite irritating: the three tiny (!) triangular knobs on the back of the unit that are used to align the finder with the main telescope. My large fingers just can’t seem

Submit Your Astro Tip! Astronomy Technology Today regularly features tips, tricks, and other novel solutions. To submit your tip, trick, or novel solution, email the following information: • A Microsoft Word document detailing your tip, trick or novel solution. • A hi-resolution digital image in jpeg format (if available). Please send your information to tips@astronomytechnologytoday.com

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to grasp them – and forget about using gloves. Certainly there must be a remedy for this situation? I began researching solutions on the Internet to see if some clever person had already found a cure, but found nothing. So, I sat down and began investigating ways to replace the knobs with larger ones, but was unable to locate just the right hardware. It was then that I decided to post a challenge on a popular astronomy forum. Amateur astronomers are a very clever and resourceful lot. I received a few replies from folks lamenting my same dislike of the small knobs, but one person, Judson Mitchell, took up the challenge and formulated a solution. After testing several options, he discovered that a specific rubber grommet fits precisely and securely over the Telrad knobs, allowing for an excellent grip. Furthermore, these grommets are cheap and readily available at most hardware stores. They measure 1/4-inch ID x 9/16inch OD x 1/4-inch thick and for approximately 50 cents my problem was solved!

There I was, trying to over-engineer a solution. Keep it simple, Steve! Now, I keep a healthy supply of these grommets in my field case and offer them to folks at star parties as my thank for Judson's solution. I hope they work for you as well.

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