The forthcoming BAA Deep Sky Section meeting prompted me to process one of my sets of deep sky data which has been hanging around. This is a wide-field Rosette, taken with a modified DSLR from Outer London over two nights in January.
The very large number of 2-minute unguided exposures has given a very smooth image from an old DSLR. Processing was with the free Deep Sky Stacker and Photoshop CS4, with gradient and light pollution colour cast removed using Gradient Xterminator. 40 flat frames and 140 dark frames were used. (The last is probably an unnecessarily large number.)
I had one problem with the processing, which I may describe as ‘dark worms’. These are not real features in space, but an artefact I guess caused by over-corrected hot pixels turing out dark in calibrated images and trailing with the stacking of slightly displaced unguided exposures. I blurred these ‘worms’ out by outlining them at 200% scale and then using Photoshop’s ‘Shape Blur’ function, but this is not a perfect treatment for them.
Click twice to see at full size.