While the weather in Scotland and the North has been terrible today, that wasn’t the case in Somerset last night. It was still, clear and moonless, so I decided to head out for some astronomy. On my previous excursion I looked at as many bright and interesting objects as possible, but the photos didn’t do them justice. This time I decided to concentrate on just one object and to do it properly.
I picked the Horsehead nebula from IC434. Last time I only had six frames and the result was very noisy. This time I took 30 frames of 50 seconds, for a total of 25 minutes. I also took 10 dark frames. As usual I used my GSO 6″ f/5 Newtonian telescope, with full-spectrum Canon EOS 600D, using a filter to cut out IR and UV but retain deep red around H-α where most nebulae emit strongly.
It’s still a bit noisy for my liking, but you can see the nebula clearly. In future I will use a polar finder scope to improve the alignment of the mount and hopefully this will give me the ability to expose for longer. I managed 50 seconds without blurring this time, an improvement on 45 seconds last time. If I can make it to a minute and a half, I can switch the ISO down to 6400. With autoguiding, which I hope to have in the new year, 2-3 minutes should be easily achievable and noise will become much less of a problem. I could also remove the IR-cut filter and scoop up more light from across the whole spectrum. Not sure how it would look, but I might be able to reduce the ISO by doing this, too.
Jonathan Gazeley 
Wow! I’d love to be able to get images like these!
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The trick with astrophotography isn’t the camera or the telescope, but the tripod and mount. Any camera and telescope can scoop up enough light given a long enough exposure, but the tripod has to be able to compensate for the rotation of the earth accurately.
My old entry level telescope mount could only track a star for about three seconds without motion blurring. My new mount (which cost more than twice as much as either the telescope or the DSLR) can track stars for just shy of a minute in its current configuration. Hopefully will be able to manage several minutes when I get hold of a guide scope so I can put my autoguider to use 🙂
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