EE DE DAR FR SI LEN N CA
I 13 20
CATCH JUPITER AT ITS BEST: WE SHOW YOU HOW
Sky at Night THE BIGGEST NAME IN ASTRONOMY
ON … SEE THEM THIS SEAS
10 WONDERS WINTER
’S THE WORLD ST E B & BIGGEST
From spectacular nebulae to glittering star clusters, don’t miss these stunning sights PLUS
Apollo 17: the 40th anniversary
Relive humankind’s final footsteps on the Moon
ALSO IN THIS ISSUE
THE BIG QUESTIONS How do we know the shape of empty space?
The Christmas survival guide HD controller: the new Vixen Go-To mount on test
Make a collimator from household items DECEMBER 2012 #91 £4.75 www.skyatnightmagazine.com
Every month, watch The Sky at Night, browse astro photos and get great software. If your coverdisc is missing, ask your newsagent for a replacement
EYE ON THE SKY NOVEMBER 07
Forever blowing bubbles This composite image captures a superbubble ripping gas clouds apart
The bulbous, blue interior of this composite image is a superbubble. Created by winds from nearby massive stars and the shockwaves from supernovae, this powerful radiation has produced a vast tear in the gas and dust clouds – shown in red and yellow in this image. Contained within the Large Magellanic Cloud (LMC), a small satellite galaxy located around 160,000 lightyears from Earth, the effects of this shockwave were captured in X-ray light from the Chandra X-ray Observatory, seen here in blue, and infrared data from NASA’s Spitzer Space Telescope, seen here in red. Optical light from the 2.2m Max-Planck-ESO telescope appears here in yellow.
ON THE CD
More stunning space images
NASA/CXC/U.MICH./S.OEY, JPL, ESO/WFI/2.2-M
CHANDRA X-RAY OBSERVATORY 30 AUGUST 2012
Our experts examine the hottest new research
Revelations from runaway stars A new way of studying stars could help to end the debate over the structure of our Galaxy WORDS: CHRIS LINTOTT This is what we think our Galaxy looks like, but it’s hard to be sure from within it
This sounds promising, but the best data available at the moment isn’t quite up to the job. It comes from ESA’s Hipparcos satellite, which recorded highly precise position and velocity measurements for more than 100,000 stars (along with less precise measurements for another two million). Despite the size of Hipparcos’s legacy, only 50 or so stars suitable for this sort of analysis were found – not enough to do the job.
MARK GARLICK/SCIENCE PHOTO LIBRARY
ne recurring theme of this column has been the difficulty of viewing the structure of our own Galaxy. It’s almost maddening that the very thing that makes the Milky Way of particular interest – our position in it – makes it so hard to study. Nowhere is this seen more clearly than in the ongoing argument about the Milky Way’s spiral arms; while there is something of a consensus settling on a four spiral arm structure, some scientists, such as the University of Sao Paulo’s Jacques Lepine, have suggested something weirder – a structure of squarer spiral arms that would make the Milky Way something rather special. To resolve this confusion, a paper by a pair of University of Hertfordshire astronomers suggests making use of special stars within our (potentially) special galaxy. Most star formation within a spiral galaxy takes place within the spiral arms. This behaviour gives the arms their distinctive blue colour in optical images – they are lit up by bright blue stars, stars that are so massive that they will not hang around for long. To determine the position of the spiral arms and to record how they have changed over time, all we need to do is to track each star back to its birthplace. This has been tried for single stars before, but among the hustle and bustle of the Milky Way’s disc it’s a little too chaotic to do easily. Instead, the authors look at an unusual population of runaway stars that exist above the disc itself. They are particularly suitable because their position makes them easier to see – they are moving quickly, so have travelled a long way from their nurseries – allowing us to trace spiral arms far from the solar neighbourhood. skyatnightmagazine.com 2013
“To find out how a spiral arm has changed over time, all we need to do is to track each star back to its birthplace”
Chris Lintott is an astrophysicist and co-presenter of The Sky at Night on BBC TV. He is also the director of the Zooniverse project
All is not lost, however. European astronomers are looking forward to the launch of Gaia, a successor to Hipparcos, later this year. Relying, like its predecessor, on careful measurement of parallaxes – the apparent shift in position of a star due to Earth’s movement around the Sun – Gaia will provide ridiculously accurate positions for objects brighter than mag. +15.0. The accuracy of their positions will be 24 microarcseconds – the width of a human hair 1,000km away. This data will enable a host of scientific projects, ranging from studies of stellar evolution through to the detection of exoplanets and probing the dark matter distribution of the Milky Way. Thanks to this paper, we can now confidently expect that it will also shed light on the spiral structure of our Galaxy; let’s hope for a successful launch.
CHRIS LINTOTT was reading… High Galactic latitude runaway stars as tracers of the spiral arms by H D V Silva and R Napiwotzki. Read it online at http://arxiv.org/abs/1302.0761
diary The Sky at Night team learn all about meteorites and get some great views of Saturn, but miss seeing Comet C/2011 L4 PANSTARRS, writes Paul Abel
BBC, PAUL ABEL X 4
eteorites! These chunks of space rock are large enough to have survived entry through our atmosphere and made it down to the ground, thus ending – often in dramatic style, like the recent Russian meteorite – what may have been a journey of many thousands of years. As they are asteroids or pieces chipped off the neighbouring planets and the Moon by collisions with asteroids, they can tell us a great deal about conditions in the early Solar System, and we were lucky enough to film meteorites and their stories for April’s Sky at Night. For this episode the team split up and travelled to different locations. Chris Lintott and Lucie set off to the Natural History Museum, while Jon, Pete, Chris North and myself were to be based in Wiltshire. Chris interviewed Natural History Museum curator Dr Caroline Smith, who showed him the impressive collection of meteorites the museum has obtained over the years. I’m quite envious that Chris got to hold the Tissint meteorite – an ancient piece of Mars which has provided yet more evidence that there was once running water on the planet. To be honest, it was probably for the best since it would only be a matter of time before I dropped the thing and made this rare artifact even rarer! Also at the Natural History Museum, Lucie interviewed Anton Kearsley, who found what looked like a plain, boring skyatnightmagazine.com 2013
rock in the wilds of Australia. However, investigation of this unassuming rock with an electron microscope unlocked its geological secrets and revealed a fascinating story – it turned out to be a fragment from the Sea of Tranquility on the Moon, an incredibly rare find.
Jane Fletcher does a sound and camera test
Any old iron? There was one more interview to be done for this episode, with Prof Colin Pillinger. He told Jon the tale of the Danebury meteorite, a space rock unearthed during an archaeological dig at the Iron Age hill fort of Danebury in east Hampshire. Colin wanted to see if this meteorite was part of the Lake House meteorite, which had spent many years outside the front door of a stately home in Wiltshire. Alas, the Danebury meteorite turned out to be only a few thousand years old, whereas the Lake House meteorite seemed to be in the order of 32,000 years old. It may well be the oldest meteorite in England. Filming for the rest of us took place on 14 March. There was much to do – Pete and myself were to record a beginners’ guide to observing Saturn to coincide with
Production coordinator Ali Suker discusses the filming sch edule with Peta and Steve Bos ley
its opposition at the end of April. Jon and Chris North, meanwhile, recorded Space Surgery, a new feature in which they answer viewers’ questions on subjects ranging from observing to cosmology. There was one other thing
Next time you look at a star, let your imagination run riot: some of them probably have planets like these in orbit
Without Kepler, what hope do we have of finding a second Earth? Govert Schilling reports on our progress
e live in a remarkable age. A few centuries ago, ancient mariners explored new continents on our home planet. A few decades ago, interplanetary probes reported on some of the other worlds in our Solar System. But today, astronomers are discovering a bewildering multitude of planetary systems accompanying stars other than our own. Our Solar System is not unique. Earth may not be alone. In fact, exoplanet researchers now know that planetary systems are the rule rather than the exception. At least
50 per cent of all stars have one or more planets with orbital periods of less than 100 days. Even one of the Sun’s nearest neighbours, Alpha Centauri B, has recently been reported to harbour a planet slightly more massive than Earth – although a subsequent analysis of the data by another team failed to confirm its existence. Likewise, most of the stars in the night sky are probably suns shining down on alien worlds. Buried in the data collected since 2009 by NASA’s Kepler space telescope – which ceased operations in May – may well be a true Earth analogue: a small, rocky,
ocean-bearing habitable world orbiting a quiet, Sun-like star. What’s more, says Sara Seager, professor of planetary science at Massachusetts Institute of Technology, “for the first time in history we have a chance of detecting signs of life on other worlds”. ABOUT THE WRITER Govert Schilling is an astronomy writer. He co-wrote Europe to the Stars – ESO’s First 50 Years of Exploring the Southern Sky.
PERFECT YOUR IMAGING APRIL 41 To capture images as impressive as this wide-field shot of Orion’s sword, you’ll need the right equipment
TAKE YOUR ASTRO IMAGING
Steve Richards explores several ways you can go from capturing good astro images to great ones
strophotographers constantly strive to improve their images by whatever means they can – it’s in their nature to do so! These improvements normally come about in small steps made possible by using longer exposures, better processing techniques, improved focus, better tracking, more sensitive cameras, exotic filters and better optics. Each small change adds to the whole, so that better contrast is captured in dim galaxies and nebulae, sharper images with greater colour saturation are produced, star
shapes are improved and hitherto unseen features are revealed. So what do you need if you really want to take it up a notch? Here we detail some of the kit you can use to help take your astro imaging to the next level. ABOUT THE WRITER Steve Richards is an expert deep-sky observer and a dedicated astrophotographer, who compiles the Deep-sky tour every month.
If you’ve captured some great astro images lately, why not submit your best photos to Astronomy Photographer of the Year 2013? The world’s premier astro imaging contest is now open to entries. It showcases the best of the year’s astro images in categories including ‘Earth and Space’, ‘Deep Space’ and ‘Our Solar System’. Find out more at
At opposition this month, Saturn presents an inspirational sight. Pete Lawrence tells you how to get the best views and images
NASA AND THE HUBBLE HERITAGE TEAM (STSCI/AURA)ACKNOWLEDGMENT: R.G. FRENCH (WELLESLEY COLLEGE), J. CUZZI (NASA/AMES), L. DONES (SWRI), AND J. LISSAUER (NASA/AMES)
sk an amateur astronomer what got them into astronomy and there’s a good chance that they’ll tell you about their first look at the planet Saturn through a telescope. If you’ve ever done this yourself, you’ll know exactly why, but if you’ve never had this particular pleasure now is a good time to try. If you don’t have a scope of your own, get in touch with your local astronomical society and see if they can help. Saturn’s good at the moment because it’s at opposition, the time when it’s in the opposite part of the sky to the Sun, on 28 April. At opposition, Earth and Saturn are at their closest, so the Ringed Planet looks brighter and bigger than at any other time. As Saturn is naturally a fair distance away, roughly 1,340 million km (9 times farther from the Sun than Earth is) the difference is actually quite modest. At opposition Saturn will shine at mag. +0.3 and will show a globe that appears to be 18 arcseconds across. For a bit of context, by November 2013, when both Earth and Saturn find themselves on opposite sides of the Sun, Saturn will have dimmed to mag. +0.8 with a globe just 15 arcseconds across. To the naked eye Saturn resembles a bright star and can be located by using a real star of similar brightness which lies nearby. First locate the familiar pattern of the Plough. Extend the arc of this asterism’s handle away from the bowl and you will eventually arrive at the bright orange, mag. +0.2 star Arcturus in Boötes. Keep following the arc and you’ll arrive at the bright white, mag. +1.0 star Spica in Virgo. Look for a similarly bright star to the left of Spica and that will be Saturn. Study it carefully and you should see that Saturn is marginally brighter than Spica and appears yellowish in contrast to the white star. >
Jupiter may have clearer belts, but Saturnâ€™s rings are unparalleled
54 011 L4 PAN
Chris and Pete’s Virtual Planetarium
RT O N eb
Sum me r Tr ian
r os s
How to use this chart
YG NU S
On other dates, use the interactive planetarium on our website at www.skyatnightmagazine.com/interactive-planetarium
γ N o rth er n
1 APR AT 01:00 BST > 15 APR AT 00:00 BST > 30 APR AT 23:00 BST
HE A ST
When to use this chart
ON THE CD
β δ γ a
M57 Ve g
Apri Peak l Lyrids s 22 Apr
Ko β c
21 Apr 2013
01 May 2013
A Pe pril ak Vi s 1 rgi 1 nid Ap s r
VIRGO LIBRA γ
CHART CONVERSION BY PAUL WOOTTON
H UT SO
γ CENT AURU
h δ Op
Moon phases in April
Times are given for the centre of the UK unless otherwise indicated.
11 Apr 2013
NA S RO ALI COORE B
01 Apr 2013
ge α Rasal
01 May 2013
21 Apr 2013
11 Apr 2013
01 Apr 2013
ys on e
The Sun and Moon this month
η K e
1. HOLD THE CHART so the direction you’re facing is at the bottom. 2. THE LOWER HALF of the chart shows the sky ahead of you. 3. THE CENTRE OF THE CHART is the point directly over your head.
THE SKY GUIDE APRIL 55
A RIG AU
DIFFUSE NEBULOSITY DOUBLE STAR
GLOBULAR CLUSTER PLANETARY CLUSTER
k ha ir p
r Cluste Double
PE IA γ
A URS OR MIN
MOON, SHOWING PHASE
BINOCULAR FIELD OF VIEW
s id in rg Vi pr a A m 14 am s G eak P
TELESCOPIC FIELD OF VIEW
0 M98 M99 M M8 M 86 4 87
BRIGHTER THAN MAG. 0
M 9 M 6 95
MA S CO NICE E BER
11 1 ot te
R CE N CA
R IN M O
CAN VENA ES TIC
Key to star charts
DON’T MISS... 3 TOP SIGHTS
1 May M35
4 Vesta passes M35
WHEN: All month; passes M35 from 29 April to 1 May, 2 2:00 BST (21:00 UT) to 23:00 BST (22:00 UT)
THE WINTER STARS are fast disappearing, but before they go there’s one final display we want to draw your attention to. Gemini, the Twins, plays host to a rather lovely open cluster known as M35. It lies near to the foot of one of the twins, not too far from mag. +3.3 star Propus (Eta (h) Geminorum). At mag. +5.0, M35 can be seen with the naked eye if the sky is dark and clear, but binoculars will give you a better view. Towards the end of the month, M35 can be found low in the western part of the sky. As the sky gets properly dark
around 23:00 BST (22:00 UT) on 30 April, the cluster is about 15º above the horizon. If you can get a look at M35 at the end of April you should also be able to catch a glimpse of minor planet 4 Vesta passing by. At mag. +8.4 on 30 April, binoculars should reveal this 500km body fairly well. At the start of the month, 4 Vesta will be visible in slightly darker skies, nestled between the two horn stars of Taurus. Its passage throughout April then takes it straight towards M35. On the evening of the 29th, 4 Vesta will be
NGC 2158 29 Apr
Minor planet 4 Vesta will pass within half a Moon width of open cluster M35’s centre at the end of April, before heading on to Collinder 89
right next to the southwest border of the open cluster. On the 30th, it passes through M35’s southern extremity, separated from the centre of the cluster by 0.25º – half the apparent diameter of the full Moon. For reference, M35 itself has a diameter roughly equivalent to the
8 May 7 May 6 May 5 May
2 May 1 May 30 Apr 29 Apr
28 Apr 27 Apr
PETE LAWRENCE X 4
The path of 4 Vesta from 26 April to 7 May; positions shown are for 22:00 BST (21:00 UT) on each evening
NEED TO KNOW
An open cluster is a group of stars that formed together in the same cloud of gas and are gravitationally bound to each other.
apparent size of the full Moon in the sky. On 1 May, 4 Vesta exits the cluster from the southeast, continuing its passage into Gemini. There’s no scientific relevance to this event, but as long as you can locate M35 in the sky, it does give you a good opportunity to see the minor planet if you’ve never seen it before. Binoculars or a small telescope will not show any detail on 4 Vesta, as it’s too small and too distant for this. On 30 April, the minor planet will be a fraction over 3 AU from Earth – around 451 million km. What you’ll be looking for is a dim star-like object not too dissimilar to the cluster stars themselves. One way to make sure you’re looking at 4 Vesta is to sketch or image the cluster over the nights mentioned. If you see a ‘star’ moving through the southern extremities of M35, that will almost certainly be the minor planet.
THE SKY GUIDE APRIL 59 N
MARE NECTARIS (600KM NORTHWEST)
RHEITA VALLIS RHEITA
YOUNG YOUNG D MALLET C MALLET D REIMARUS A
Vallis Rheita TYPE: Crater chain SIZE: 480km long, 38km wide AGE: Between 3.9 to 4.6 billion years old LOCATION: Latitude 42°S, longitude 51°E BEST TIME TO OBSERVE: Four days after new Moon (evening of 14 April) or three days after full Moon (after midnight on 27 April) RECOMMENDED EQUIPMENT: 2-inch telescope
The Vallis Rheita may be a result of the impact that created the Mare Nectaris, not visible above
MOONWATCH With Pete Lawrence “The northern part of the valley is created by a number of craterlets about 24km across. These overlap, creating a continuous path to the southeast” THE PHRASE ‘LUNAR valley’, probably conjures up an image of a steep walled groove cutting through the surface of the Moon. Indeed, there are many examples like this on the lunar surface, but the Vallis Rheita is something different altogether. This feature is made up of a string of craters, all apparently connected and all running in a more or less straight line across the lunar surface. The Vallis Rheita gets its name from the 71km-wide crater Rheita, which lies to the east of the northern end of the chain. Southwest of Rheita is another crater, Metius, slightly larger at 90km wide, and together they act as guardians over the northern end of the valley.
When you realise you’re looking at a crater chain, the shape of the Vallis Rheita becomes obvious. The northern part of the valley consists of a number of craterlets approximately 24km across. These overlap, creating a continuous path to the southeast. Eventually, they meet and feed into another crater, 71km-wide Young. Young’s southern edge touches 46km-wide Young D, which appears to mark Vallis Rheita’s southern end. However, if you can work through the jumble of craters, the valley does continue beyond Young D, leaving the southeast wall of 28km-wide crater Mallet C. Here the nature of the valley changes into a narrow channel measuring
about 6km across. It runs for about 40km before reaching 42km-wide crater Mallet D and for another 75km after it, before properly ending at 29km-wide crater Reimarus A. Where did the Vallis Rheita come from? The most probable explanation is that it formed as a result of the impact that created the Mare Nectaris. This 360km-diameter lunar sea lies about 600km to the northwest and the craters that form the Vallis Rheita align in a radial fashion – sort of. The Vallis Rheita bends in the middle as it passes Mallet C. If you draw a line along the narrow southern portion of the valley, it is certainly radial to the main area of the Mare Nectaris. However, the wider northern portion seems to align with the southern extremity of the sea: it’s on a tangent with the outer rim of the basin. It’s likely that a large piece of debris flung out as the Mare Nectaris formed resulted in the multiple impacts that created Vallis Rheita, but why there is a bend isn’t well understood. When the illumination is right, it’s fascinating to journey along the valley. The best time to do this is four days after new Moon or three days after full, which this month occurs on the evening of 14 April, or after midnight on 27 April. skyatnightmagazine.com 2013
ON THE CD
More of your stunning images
This month’s pick of your very best astrophotos PHOTO OF THE
p NGC 891 PETE RICHARDSON SOMERSET, 8 SEPTEMBER 2012 Pete says: “This has to be my favourite edge-on galaxy. I love the dramatic dust lanes, bright central region and overall symmetry this galaxy displays. It’s certainly one I will return to again and again in the future.” Equipment: Orion Starshoot Pro V2 one-shot colour CCD camera, Meade LX200-ACF 12-inch reflector Sky at Night Magazine says: “The details and colours Pete has captured in the dusty disc of this enigmatic galaxy are superb. We particularly like the nicely balanced star colours and the handful of galaxies that are visible in the background.” About Pete: “Astronomy has been an interest since childhood, mainly due to my late father who had a keen interest in the subject. He helped to fire my sense of wonder in all things astronomical. Just over two years ago I built my own observatory, which was the best thing I ever did to support my love of astro imaging. I enjoy both deep-sky and planetary work.”
p Star trails NICK RICHARDSON, VICTORIA, AUSTRALIA, JANUARY 2013 Nick says: “This image was taken with a pretty full Moon, but I like the almost-daylight feel to it. I also like the softness of the ocean giving the image an overall serenity. It was great to go out for the night with just a camera and a tripod instead of the usual gear.” Equipment: Canon EOS 1100D DSLR camera, Tokina 11-16mm lens
HOTSHOTS JUNE 29
The aurora borealis STEVEN MCCONNACH THURSO, 17 JANUARY 2013 Steven says: “This picture shows a nice but short-lived aurora on 17 January. It was a very nice sight in the sky, I just wish it had lasted longer.” Equipment: Canon EOS 500D DSLR camera
The Pleiades BOB FRANKE, ARIZONA, US, JANUARY 2013 Bob says: “It took eight nights to accumulate the 670 minutes of LRGB data for this winter classic. The Pleiades is probably the most famous cluster in the sky and is easily visible with the naked eye. However, it is best viewed with binoculars or a small telescope.” Equipment: SBIG STF-8300M CCD camera, Takahashi 106ED telescope, Baader LRGB filters, Losmandy G11 mount
▲ The International Space Station MARK WHITE, CHESTERFIELD, 19 FEBRUARY 2013 Mark says: “This image is probably one of my favourite astro photos. I had always wanted to capture the ISS and the Shuttle but unfortunately never managed to get the latter, so this more than makes up for it. I’m impressed by the detail I managed to capture with a small 6-inch mirror, especially the capsules and labs.” Equipment: DMK monochrome CCD camera, Sky-Watcher Explorer-150PDS Newtonian reflector, 2x Barlow lens, Sky-Watcher HEQ5 Pro mount
Brush up your practical astronomy prowess with our team of experts
Contents The guide
Scope doctor Lost in space
We explore the true size of the Solar System
Organise your eyepieces with a six-space rotating rack
Learn how to draw open cluster NGC 6939
Steve Richards answers your astro equipment queries
Keith invents a verb, much to the chagrin of the OED
The scale of the Solar System With Olivia Johnson
There’s more to our home than eight planets and an asteroid belt
DETLEV VAN RAVENSWAAY/SCIENCE PHOTO LIBRARY,
MIKKEL JUUL JENSEN/SCIENCE PHOTO LIBRARY
The Solar System is mind-bendingly vast: the major planets stretch out to 30.1 AU from the Sun, and they are just a fraction of our home in space
hough it is often referred to as our ‘local neighbourhood’ in space, our Solar System is staggeringly big in human terms. If you look through a small telescope at the bright shape of Saturn, you will see a planet that is well over a billion kilometres away. To travel that distance on Earth, you’d need to go all the way around the globe nearly 800,000 times. Yet the familiar planets are just the innermost jewels of a skyatnightmagazine.com 2013
much larger system containing dwarf planets, comets and more. Beyond the orbit of Neptune lies the Kuiper Belt, a huge and largely unexplored debris field containing at least three dwarf planets. Even farther afield is the heliosphere, a bubble in the interstellar gas and dust that fills our Galaxy blown by a fast stream of particles from our Sun. Farther still is the theorised Oort Cloud, another vast collection of debris, which
some astronomers believe could extend trillions of kilometres to the limit of the Sun’s gravitational influence. Measuring such huge distances is a daunting task, but astronomers have been trying for a surprisingly long time. The Ancient Greeks used naked-eye observations to estimate the distance to the Moon and the Sun in terms of Earth radii. From the 17th century through to the 19th century, observations of parallax – the apparent
SKILLS APRIL 83
Sketching Crater Albategnius
With Carol Lakomiak
NEED TO KNOW STEP 1 Carefully draw a basic outline of Albategnius’s main features with an HB pencil, also adding where the shadows are. Fill in the shadows with a 4B pencil. It’s important to draw the shadows now because they move rapidly and can cause confusion as the sketch progresses.
NAME: Crater Albategnius TYPE OF OBJECT: Lunar crater CONSTELLATION: In Cancer on the suggested night RA: N/A DEC.: N/A TIME TO SKETCH: The night of 18 April EQUIPMENT: 4-inch telescope or larger; H, HB, 4B pencils; blending stump; sandpaper; hard and soft art erasers FIELD OF VIEW: 337 square kilometres at 404x magnification
ALL PICTURES: CAROL LAKOMIAK
his month’s target is named in honour of Al-Battani, a brilliant astronomer and mathematician whose works were quoted by Nicolaus Copernicus and Tycho Brahe among others. He lived from 858 to 929 in Upper Mesopotamia, an area that straddles what is now northwest Iraq, northeast Syria and southeast Turkey. One of his most famous astronomy achievements was determining the length of a year to within a few minutes of our modern calculations. Crater Albategnius is located in the central highlands of the Moon’s southern hemisphere. It contains a few northern craters and a central peak, and is overlapped by Crater Klein on its southwest wall. It’s easy to get carried away when making a lunar sketch, so study Albategnius in the eyepiece for a while in order to determine how much of it you want to sketch and which features to include. While doing this, you’ll notice that sunlight reflects more brightly from some areas than others – this is the ‘albedo’ mentioned in steps two and three. On the suggested sketching night, the Moon will have reached its highest point
just before sunset, so the earlier you can start sketching the better. You can even begin before sunset if you’d like. The view won’t be the best, but it will be sufficient enough to get the basic outline completed. If you begin before sunset though, don’t draw the shadows until you can see their edges quite clearly. Since Albategnius’s central peak is centrally located, begin there and work your way around, judging each feature’s shape and placement as accurately as possible. When drawing your basic sketch, be sure to include the borderlines of bright areas on the walls of both Albategnius and Klein. To remove the lines later, work a soft eraser to a point and dab off as much of the graphite as possible. Then with a blending stump, use small circular motions to blend any residual lines into the sketch. Some final tips. If an area seems a bit dark, flatten a soft eraser and dab layers of graphite from the sketch until the albedo is adjusted. Finally, clean any stray smudges from bright albedo areas with the corner of a hard eraser.
STEP 2 Draw the darker of the albedo areas by holding your HB pencil flat against the paper, then use a blending stump to gently push the graphite into the paper’s texture. The blending process will make the graphite appear darker, so be sure to use it sparingly.
STEP 3 Clean the blending stump on piece of sandpaper. Using an H pencil, apply the lighter albedo areas with the same technique as in Step 2. Brighten the white areas with a hard eraser. If necessary, remove excess graphite with a soft art eraser.
With Steve Richards
Our resident equipment specialist cures your optical ailments and technical maladies
How can I connect a Micro Four Thirds digital camera such as a Panasonic GX1 to a Sky-Watcher Skymax 127 Maksutov-Cassegrain?
STEVE’S TOP TIP
nt in a What is the best way to power a mou remote location? ous amounts Modern Go-To mounts require copi such as ies of power, as do common accessor t mos The . eras dew heaters and CCD cam at use for ce sour er pow able conveniently port such ’ tank er ‘pow h 17A a is tion loca a remote Sky-Watcher, as those produced by Celestron and er sockets. light r ciga with as these come complete e is nativ alter DIY ier heav er A useful but rath een betw city capa a with ery batt re a 12V leisu sufficient 75Ah and 110Ah. This will provide but you ons, sessi power for several observing it keep to er ition cond ery need a proper batt . ition cond in tip-top
DR MARK W JONES
How do I balance my 8-inch Sky-Watcher Dobsonian when I have a DSLR camera attached to the focuser? ERIC WILSHAW
PAUL WHITFIELD X 2
The Sky-Watcher Skymax 127 has a T-thread on its rear, which you can use to attach a Micro Four Thirds camera
The camera you mention, the Panasonic GX1, is attractive for lunar imagers as it has interchangeable lenses that comply with the Micro Four Thirds mounting system. Whereas a typical DSLR camera has a back focus (the distance between the mounting flange and the focal plane) of 45mm, the Micro Four Thirds standard requires a much shorter distance of 20mm. This means that the camera can be made smaller and the shorter back focus can make it easier to attach the camera to a telescope. The GX1’s sensor size is 17.3x13.0mm (21.6mm diagonal), which is smaller than the sensor of a typical DSLR camera. Combined with the 1,500mm focal length of the Sky-Watcher Skymax 127,
you would capture a field of view 39.6 arcminutes by 29.8 arcminutes – just enough to capture the disc of the full Moon at apogee, its farthest distance from Earth. Your telescope has a 1.25-inch ‘visual back’ that the diagonal and eyepiece are attached to. The visual back also has a T-thread around it. To connect your GX1 to the telescope, screw a Micro Four Thirds to female T-thread adaptor, available from most good astronomy retailers, onto the visual back. Don’t be concerned if there is insufficient extension between the camera and the visual back to achieve focus. This can be simply rectified by adding a T-extension tube.
Dobsonian mounts like the Sky-Watcher SkyLiner 200P, right, rely on the very fine balance of the optical tube, often helped by tension adjustment on the altitude axis. However, the additional weight of larger eyepieces or DSLR cameras can tip this balance too far, making it difficult for the mount to hold altitude. You can prevent this by adding weight at the primary mirror end of the tube to counteract the additional weight at the front. One of the more elegant and adjustable solutions involves the rubberised roof magnets that are often used to fix taxi or driving school signs to the roofs of cars. Attach one of these magnets to the side of the telescope, near its base. Then add cut sheets of metal, drilled to match the bolt projecting from the centre of the magnet, until balance is restored. All-round gear guru Steve Richards is a keen amateur astronomer and astrophotographer. He loves nothing more than tinkering with telescopes and accessories.
Email your queries to firstname.lastname@example.org skyatnightmagazine.com 2013
TOP LUNAR WONDERS
Summer is an ideal time to get to know the Moon
VALLIS ALPES This valley cuts across the Montes Alpes mountain range. It is best seen around first quarter or one day before last quarter. For a challenge, look for the fine rille that runs along the valley floor.
PLATO This dark-floored crater is very prominent in any instrument. Plato’s floor is pocked with many smaller and harder to spot craters – look for them around nine days after new Moon and around last quarter.
MONS PICO AND MONTES TENERIFFE The Montes Teneriffe emerge from the lava floor of the northern Mare Imbrium. They stand over 1km high, casting long shadows when the light is shallow. Mons Pico is to the south.
ONE OF THE biggest reasons for not putting your telescope away has to be our stunning neighbour, the Moon. Yes, it graces our skies every month. Yes, its ever changing phases are visible throughout the year. But it doesn’t suffer in the light summer skies, making this an ideal time of year to get to know it in all of its glorious detail. Even viewing the Moon with the naked eye can provide beautiful sights if it lies near to any bright stars or planets, such as Spica and Saturn, in the bright evening twilight – which is exactly what happens on 16 July and 12 August. In the couple of hours or so before sunrise on the morning of 4 August, you can even spot it below Jupiter and Mars as a slender crescent. Binoculars allow you to view detail on the Moon more easily, particularly the larger features such as impact basins, the
Mare Crisium, the Mare Tranquillitatis and the Mare Imbrium. During the days either side of full Moon you can also spot some of the more prominent ejecta ray systems, such as those from the craters Tycho and Copernicus. Once you switch to a telescope, the level of detail becomes stunning. As the terminator sweeps across the lunar landscape look out for dramatic views of showpiece craters like Plato, as well as crater groups such as the Theophilus trio, comprised of the craters Theophilus, Cyrillus and Catharina. More features reveal themselves with increased magnification and aperture size: look out for tiny craters on the dark floor of Plato, cracks such as the Rima Hadley and the many lunar domes that are scattered across the Moon’s surface.
A sinuous rille lying close to the Apennine mountain range and Crater Archimedes, famous for being visited by the Apollo 15 astronauts in July 1971. The rille resembles a meandering river.
RUPES RECTA This 110km-long linear fault, often called the ‘Straight Wall’, is situated on the east bank of the Mare Nubium. It is best viewed either a day before first quarter or at last quarter.
TYCHO Crater Tycho has steep ramparts, a central peak and an extensive ejecta ray system extending from it. It is a particularly stunning sight in large-aperture scopes.
THE BIG QUESTIONS
Our occasional series tackling the enduring questions of the Universe returns. Over the next three months, theoretical physicist Mike Evans will look at something every stargazer wants to make the most of – examining our perceptions of it, where it comes from and how it can best be captured – as he asks:
s i t a Wh
MATTHEW ANTONIO/WWW.123RF.COM LIGHT ILLUSTRATION BY PAUL WOTTON, THINKSTOCK X 11
e spend sleepless nights and the kids’ university fund trying to catch the stuff, but what exactly is it? The ancients argued long and hard about the nature of light. Greek philosopher Empedocles somehow convinced the ancient world that the goddess Aphrodite lit a fire inside the human eye, making light shine out of it. I know it is easy to scoff with the benefit of hindsight, but I suspect old Empedocles (who also believed that we breathe through our skin) was the loudest rather than the brightest philosopher in Ancient Greece. More successful thinkers of antiquity worked out some of the principles of optics. Euclid, Ptolemy and the wonderfully named Hero of Alexandria all had brilliant insights skyatnightmagazine.com 2013
into the geometry of light rays, allowing them to design useful mirrors and predict where shadows would fall. But, without the experiments and theories of modern physics, no one knew what light was made of until much more recently. Even the great Isaac Newton got it wrong. Because light travels in straight lines, he thought it must be made of particles called ‘corpuscles’, like tiny bullets that ricochet off mirrors and leave shadows in areas that are shielded from them. Newton can be forgiven for believing this, because the idea works very nicely. It even seems to fit with the modern concept of photons, but actually, light’s not like that at all – we’ll talk more about photons later. Newton had a running argument with Dutch genius Christiaan Huygens,
who believed that light was a kind of wave. If you’ve ever visited a duck pond, you’ll know that waves can travel in straight lines too; the bow-waves behind our feathered friends advance steadily across the surface until they reach the bank, where they can get reflected if the side of the pond is hard and flat, reminiscent of a mirror. So waves sometimes travel in straight lines. But sometimes they don’t. When the waves from a storm at sea arrive at a harbour entrance, they don’t just continue in a straight line to the quayside. Instead, the lapping at the harbour-mouth creates ripples that spread out, disturbing all of the water in the harbour. This spreading out when waves pass through an opening is called ‘diffraction’. It explains why you can hear people talking in the next room >
REVIEWS JUNE 89
Reviews Bringing you the best in equipment and accessories each month, as reviewed by our team of astro experts
HOW WE RATE Each category is given a mark out of five stars according to how well it performs. The ratings are:
★★★★★ Outstanding ★★★★★ Very good ★★★★★ Good ★★★★★ Average ★★★★★ Poor/Avoid
We find out how Orion has made this man-sized Dobsonian portable
This month’s reviews First light
iOptron SkyTracker camera mount with polarscope
Orion SkyQuest XX16g Dobsonian telescope
Mesumount 200 with Go-To hand controller
We rate four of the latest astronomy titles
Gear PAUL WHITFIELD X 4
Including this 1.25inch Hyperflex-7E2 zoom eyepiece
Find out more about how we review equipment at www.skyatnightmagazine.com/scoring-categories skyatnightmagazine.com 2013
FIRST light Orion
SKY SAYS… The XX16g has a big aperture for great views but also offers the travelling convenience of a smaller telescope
A exceptionally solid man-sized telescope with great Go-To capabilities
WORDS: MARTIN LEWIS
VITAL STATS • Price £3,299 • Optics 406mm (16 inches), f/4.4 • Mount Dobsonian, computerised altaz Go-To • Focuser 2-inch dual-speed Crayford • Hand controller SynScan controller • Extras 28mm eyepiece, 12.5mm illuminatedreticule eyepiece, zero-power EZ finder, 2-inch to 1.25-inch adaptor, focus extender tube • Weight 79kg • Power 12V DC 2.1A (not supplied) • Supplier The Wideccreen Centre • www.widescreencentre.co.uk • Tel 020 7935 2580
arge aperture Dobsonian telescopes are ideal if you want spectacular deep-sky views. But what if you also want Go-To ability and a scope that fits easily in your car so you can travel with it to darker skies? If you want all of those things, then Orion’s new SkyQuest XX16g could be for you. The telescope has a 16-inch primary mirror with enhanced reflectivity coatings, as well as full Go-To capability and motorised tracking. But it can also be broken down into separate parts that will fit in an average car, allowing you to take it away from the city lights and make the most of that big aperture. The owner’s manual is nicely detailed. Photos showed exactly what is packed in each box and give comprehensive step-by-step assembly and operating instructions. Putting it together is a straightforward process, although the manual shows the differently designed cell for the smaller XX12g. Disassembling it into manageable parts to take outside or load into a car takes 5-10 minutes, while reassembly takes 20-25 minutes. The ground board is quite bulky, and slightly larger and heavier than perhaps it could have been. A fair amount of the assembly time was spent
ALL PHOTOS: PAUL WHITFIELD
THE SUM OF ITS PARTS Due to their sheer size, large-aperture commercial Dobsonians often present practical difficulties when it comes to moving them between observing sites. Orion’s XX16g overcomes many of these difficulties with an innovative design that enables it to be broken down into smaller and lighter parts. Like most big Dobsonians, the truss tubes separating the top and the bottom of the main tube can be easily removed, which saves considerable space. Where the XX16g is different is with its large and heavy rocker box, which houses
the azimuth and altitude bearings. This rocker box can be separated into the baseboard and three side panels by undoing a set of hand bolts that screw into mating threaded bosses. This great idea means that the rocker box packs down flat and the whole telescope can be readily fitted inside a standard car. What’s more, it also means you can load and unload the telescope yourself without needing a second person to help, or resorting to the use of ramps and wheelbarrow handles like some owners of other big Dobsonians.
attaching the nine 1kg counterweights, which help balance the head unit that houses the secondary mirror. A lighter, less overly robust head would have eliminated this task and saved further weight. Minor collimation adjustment of the main mirror is always needed before observing – it’s a relatively painless procedure and fully explained in the manual. Setting up the Go-To requires a two-star alignment process. This involves manually centring a bright star in the supplied illuminated crosswire eyepiece, automatically slewing to the second and then using the motor control buttons to centre this second star.
Smooth operator We found the whole Go-To system to be wellbehaved and relatively simple to use. You can use the motors to automatically move to new objects or you can release the friction clutches and push it most of the way before finishing off with the motorised Go-To. If you do decide to push it, the closed-loop control means you won’t lose alignment when you unlock the bearing clutches. Whichever method you use, the accuracy seems to be the same and when >
FIRST LIGHT JUNE 95
FOCUSER The 2-inch Crayford focuser is a well-made, smooth-running unit, and includes a 10:1 speed reduction knob. A 2- to 1.25-inch adaptor is supplied. The focus position is quite a distance from the body of the telescope, which means having to use the supplied extender tube to achieve focus for some eyepieces.
HAND CONTROLLER The SynScan hand controller is the heart of the scope’s control system. It has a clear LCD display and tactile illuminated buttons – the four directional cursor keys offer manual control of the two drive motors. It has a database of 42,000 objects, including the Messier, IC and NGC catalogues, and supports custom lists.
OPTICS The enhanced reflectivity 16-inch primary mirror has a strongly convex back and is significantly thinned down at the edges, reducing weight and allowing it to reach ambient temperature more quickly. The mirror is mounted on its thick centre, which simplifies the support mechanics. The secondary obstructs 22 per cent of the view.
GO-TO MOUNT One of the great features of this scope is the Go-To system, which allows the scope to automatically seek out any object you select from the handset’s database. The motors continue to smoothly track the object once centred.
Make a 50mm eyepiece With Simon Dawes
Turn a redundant SLR lens into a champion accessory
TOOLS AND MATERIALS
Use epoxy resin glue to stick your barrel to the front of the lens. MASKING TAPE AND PEN
To mark the centre of the rear lens cover prior to cutting the eyehole. OPTICS
You’ll need an old lens with a focal length up to 50mm to convert into an eyepiece. Ideally it will have its original rear lens cover. You can use any SLR lens with a focal length up to 50mm to make this eyepiece for next to nothing
ALL PICTURES: SIMON DAWES
his month’s How to follows in a long tradition of making telescope accessories from parts originally intended for a different use. Here we’re taking old SLR (single lens reflex) lenses that are no longer needed in the digital age and putting them to use as telescope eyepieces. Eyepieces come in many shapes and sizes, from the simple single-element Kellner to more complex multi-element zoom affairs. However, with little or no optical experience, it is possible to adapt old SLR camera lenses into eyepieces that will perform well – not to mention give you the satisfaction of using a homemade accessory that costs next to nothing to make. skyatnightmagazine.com 2013
You can use SLR lenses with focal lengths up to about 50mm for this project. The thing you need to watch out for is the size of the exit pupil, which is the size of the beam of light that emerges from the eyepiece. A diameter greater than 7mm will result in a beam of light larger than your eye’s fully dilated pupil – your eye will not be able to collect all of the light being gathered by the eyepiece, so effectively the image will appear dimmer. Thankfully, the exit pupil is not dependent on the optical design of the telescope or eyepiece. It is easily calculated by dividing the focal length of the lens (in millimetres) by the focal ratio of the telescope. For example, a ‘standard’ 50mm lens on an f/8 telescope will yield an exit pupil of 6.25mm.
A vice, electric drill, hole cutter and pilot drill bit will allow you to make a suitable hole in the rear lens cover; use a hacksaw to remove any levers. TUBE
Use a piece of tube 1.5 inches long for the barrel for your eyepiece. It needs to be 1.25 inches in diameter so you can slot the finished eyepiece into a focuser.
Having chosen your lens, you need to modify it for telescope use. When your eyepiece is complete you will be looking through the rear of the lens – the end that connects to the camera. You will need to glue a 1.25-inch diameter tube to the front of the lens to act as the eyepiece barrel, allowing you to slot it into a telescope
104 GEAR MAY
Vincent Whiteman rounds up the latest astronomical accessories
4 1 Q-Turret Quadruplet Eyepiece Revolver
Price £70 • Supplier The Widescreen Centre 020 7935 2580 • www.widescreen-centre.co.uk Attach this four-position eyepiece holder to your setup and you’ll be able to switch between fixed focal length eyepieces on the fly. Eyepieces shown are not included.
2 Baader 6mm Classic Series Orthoscopic Eyepiece Price £49 • Supplier First Light Optics 01392 826133 • www.firstlightoptics.com
This 6mm orthoscopic (distortion free) eyepiece offers a 50º field of view and has an inset rubber eye cap.
3 Vixen Polarie Polar Scope
Price £176 • Supplier 365 Astronomy 020 3384 5187 • www.365astronomy.com Designed to accompany Vixen’s Polarie Star Tracker, this red LED illuminated 6x30mm polar scope features a spirit level, time and date circles, and a meridian offset scale for different time zones.
4 Universal Dovetail Mounting Plate
Price £22.99 • Supplier Nipon Scope and Optics 0844 3187890 • www.nipon-scope.com This plate features adjustable screw positions, allowing you to secure a telescope to an equatorial tripod.
5 Outdoor Sports Mitten
Price £45 • Supplier SealSkinz 01553 817990 • www.sealskinz.com Keeping your hands toasty is critical for a good night’s observing. These mittens are designed for warmth, comfort and strength, with a fingerless option for when you need to adjust your setup.
6 Orion Deluxe Mini Guide Scope with Helical Focuser Price £169 • Supplier SCS Astro 01823 665510 • www.scsastro.co.uk
Featuring a helical focuser for accurate guide star focusing, this 50mm guide scope also doubles as a finderscope. It attaches to telescopes through a dovetail bracket.
106 EXPERT INTERVIEW JUNE
WHAT I REALLY WANT TO KNOW IS…
Can robots build us a base on Mars? André Schiele is developing technology that will allow machines to work for humans in space INTERVIEWED BY PAUL SUTHERLAND
obots are becoming more and more important in space exploration. They are in use already – the NASA rovers trundling about on Mars are robots, for example. I’m working at ESA to help improve the technology that allows robots to work together to perform more complex tasks. In the future they could help us to build bases on other worlds or mine asteroids. There are two kinds of robotic developments going on at the moment. The first is mainly for scientific projects or geological investigations exploring planetary surfaces. That started with the Sojourner rover, then Spirit and Opportunity, and now Curiosity. These Mars rovers are typically controlled from Earth in a very indirect way. Scientists and engineers on Earth plan what investigations to do, check and validate that with the robot and then, once the commands have been run through simulators, they are radioed across space to the rover itself.
Operational issues It is not practical to drive a rover in real-time from mission control because there is always a delay of up to 40 minutes between issuing a command and getting a response, depending on how far apart the Earth and Mars are in their orbits. Engineers have been working to get round this by shifting more autonomy onto the robot itself – essentially allowing more local decision-making on Mars. Late in the missions of Spirit and Opportunity, software patches were uploaded to help them avoid hazards and obstacles, for example. The other big string of robotics is used in Earthorbiting spacecraft such as the International Space Station (ISS), as well as those that capture and repair satellites or remove space debris. Because the distances are comparatively small they can be directly controlled, with time delays of 20-500 milliseconds. skyatnightmagazine.com 2013
Robonaut 2 is in operation aboard the ISS; here it is measuring air velocity in the Destiny lab module
ABOUT ANDRÉ SCHIELE Dr André Schiele founded and runs ESA’s telerobotics and haptics laboratory at Noordwijk in the Netherlands. He is principal investigator for the ISS METERON project and has helped develop technology for Mars rovers and some exoskeleton human robot interfaces.
ESA and NASA have been working together on a new type of interplanetary internet, the Disruption Tolerant Networking protocol; last year NASA astronaut Sunita Williams used a laptop to control a small ESA robot rover in Germany from the ISS. And NASA has installed a humanoid robot called Robonaut 2 on the ISS. This is the sort of robot that NASA and ESA are designing; one that will be able to carry out similar functions to astronauts, using similar tools. When humans fly to Mars we want to send robots first to prepare the way for them, performing the manual hard labour. Then when the astronauts arrive, they can wait in orbit for the robots to finish building the base where they will live and work. Only as the work nears completion will the crew need to land on the Martian surface to carry out the final touches. In Europe we have initiated a project called METERON (Multi-Purpose End-To-End Robotic Operation Network) to make controlling groundbased robots easier from space. The Mars robots will be far more advanced, but our controls need to be developed so that they are more intuitive; something like an iPhone for robots. To build a robot like this involves a number of disciplines – mechanics, electronics, motors, control algorithms and software – all of which are interrelated. If you want your rover to look at rocks and get geological information, it will look very different to a robot that you would need to set up a habitat, for example. The communications system will be equally important because these robots will have to work with each other as well as with their human controllers. But once all of the practicalities are solved, we may be able to look forward to the first Mars colony, built by robots, in 20 or 30 years time. S