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.