Travelogue
I
have have been fascinated with the night sky as long as I can remember. Observing and photographing Halley’s Comet 30 years ago from our backyard in Melbourne is a still a memorable event. In those days there were no fancy digital single-lens reflex cameras; we used film and needed the patience to develop it to see what nuances the pictures revealed that the naked eye could not otherwise see. Comets are of particular interest as they are one of the origins of meteors. They leave in their wake a stream of debris which is largely made up of particles finer than sand. When the Earth passes through such a trail, the fast speed of the particles imparts a lot of energy as they collide with the atmosphere. We see this as a flash of light as they burn up – what many of us call shooting stars, but are, in fact, meteors. (If a larger particle happens to make it to the Earth’s surface then it’s called a meteorite). The bigger the particle, the bigger the flash. Occasionally they are even bright enough to
134
volume 5, edition 5
apex experience
be seen in daylight, as evidenced recently in Russia.
meteor tracking Since the orbit of the comet is well known, it is possible to predict in advance when it will intersect the Earth’s orbit. All meteors radiate from this intersection, known as the radiant. You are more likely to see meteors in the quadrant of sky surrounding the radiant, so it is a good place to point your camera. Capturing meteors in a photograph is like imaging lightning; the shutter need only be open long enough to capture the event. How much meteor light your camera captures is determined by its aperture and ISO. Pupils dilating at night to improve night vision work exactly like aperture blades in your lens: The wider the opening, the better. The second factor, ISO, is a measure of how sensitive the camera sensor is to photons of light. The higher the number, the more sensitive and the more photons captured. Increased sensitivity, however, has a downside, as it’s
Visit us at apex.aero
Escaping clouds is one reason to consider airborne astrophotography. Another is less absorption of starlight.
Airline Passenger Experience Association