Astrophotography

It’s winter, it’s dark early, and the Arctic snap passing over the UK means it is nice and clear in the sky. Last night I went to my top-secret stargazing location in Somerset. It’s far enough to avoid the worst of Bristol’s light pollution, but there is still an orange tint in the sky. It’s not a bad compromise between darkness and convenience – in the past I’ve seen the Milky Way from this site but last night it was almost a full moon, so not much chance of seeing any deep-space objects.

Geek info: skip this block if you don’t care about telescopes.

All pictures taken with a Celestron NexStar 127 SLT Maksutov-Cassegrain telescope, f=1500mm, d=127mm, f/12. Alt-azimuth mount (sucks for astrophotography) so exposures are kept short to avoid rotation of the field of view during exposure. Camera is a Canon EOS 600D mounted at the telescope’s prime focus, no eyepiece or extra lens. I would normally use a Barlow lens or teleconverter to boost magnification but I accidentally left it at home.

First and foremost, I photographed the moon. At my telescope’s focal length of 1500mm the moon neatly fits in the frame of my crop-sensor DSLR. I also took a couple of pictures on my film-based Canon FTb. The moon doesn’t fill the frame on this camera, but I’ll be able to enjoy printing the negative in my darkroom.

Composite of 20 shots, using only the blue channel, 1/125s, ISO 100.

Then I turned my attention to Jupiter, which was bright in the sky. In the eyepiece I was clearly able to see three of the four Galilean moons but they don’t appear in any of the photographs. I’m not sure if that is due to poor focusing, or insufficient dynamic range. I’m annoyed that I accidentally left my Barlow lens at home – that would have given me three times the magnification and Jupiter would have been larger in the frame and would have better resolution. Always next time…

Composite of 36 shots, 1/160s, ISO 800.

Last but not least, I tried one of the brighter Messier objects. M45 Pleiades Cluster was visible with the naked eye so it seemed fair game in the telescope, despite the full moon. Unfortunately I underexposed mine. It should have looked like this. That picture says it was taken with seven 180-second exposures. Next time I’ll give it a bit more exposure and see if I can capture some of the nebulosity.

Composite of 33 shots, 1/5s, ISO 3200.