The Rosette Nebula
With a clear sky forecast all night last night, I decided to have a go at imaging something new last. A quick look at Stellarium showed that the beautiful NGC2237 - otherwise known as The Rosette Nebula - was perfectly positioned in the sky. So, with my son to assist, I set-up the scope and had the target centred in my field of view within 20 minutes. After ensuring the focussing was okay I initiated a series of 14 x 900s exposures, using Nebulosity 3 to control the QHY8L CCD attached to my Altair Astro Wave 115 triplet refractor. I initially tried a medium 'dither' between shots - this basically moves the scope a little between each shot to try and minimise any backlash in the mount, but it took ages to settle down for the next exposure so I cancelled that and re-started without the 'dither' option selected.
With over 3 hours of data to collect, we retired inside to keep warm and left it running. Once the imaging run was complete I decided to have a go at capturing some 'Flats'. I have not used them before, but I have a few dust spots on my optics somewhere and I was given some good advice on Stargazerslounge last week about using Flat frames to get rid of them, so I thought I'd give it a go. I don't have a light panel, but my iPad screen with a sheet of paper in-front of it to defuse the light, seemed to work well enough.
When it came to processing the image the Flats and Darks made a good job of getting rid of a lot of artifices, although there were still some that needed removing manually. It was also at this stage that I realised that having stopped the session to turn of the 'dither' option, my focussing wasn't as spot on after I restarted. As a result, the Stars were not as sharp as I would have liked. I also have doubts about the field flattener - it is probably something to do with the spacing between flattener and CCD, which needs to be accurate down to a very small tolerance - more work required there I think. However, after a little processing in Photoshop, the final result is actually fairly reasonable I think.
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| The Rosette Nebula (NGC2237) - 14 x 900s, Altair Wave 115 Triplet and QHY8L |
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