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Not sure what you mean by RGB aligned as this is a colour DSLR so the output is already colour. Do you split the image into colours and process separately? (Some DSLR imagers do that).
The dust is removing nicely but there still seems some vignetting present, at least in the small thumbnails.
Did you desaturate the flat to get a mono? I was wondering about that the other day from this post. If you use a flat that is mostly blue and flats are dividing would'n't that weaken the blue channel in the image?
Perhaps you can do a test and find out. Perhaps desaturating your colour flat may work. There are DSLR specific astro sites like digitalastro yahoo group or Images Plus discussion group where these sorts of things no doubt are debated.
Also you need to clean your camera - that's pretty dusty and cleaning your gear regularly is a lot easier than flats!
My current procedure for flats is to take several and then max/min clip combine in CCDstack then when I apply them to the image I select the bias subtract option.
There is a paper by Richard Crisp on flats. He is a semi conductor engineer and an expert in this field. Apart from the complex maths etc (best to skip over that unless you are into maths) it is quite informative.
He basically states that with CCDs (it should be similar for DSLRs) that they are very linear (meaning they respond in a predictable straight line type way at different light levels). He recommends taking a quite bright flat and a flat dark subtract (a dark of the same duration and temp as the flat) to give the minimum amount of noise the flat introduces into the image.
Flats can be a tricky area of processing so its worth a thread by itself as there are bound to be different approaches from various imagers here.
Greg.
Greg.
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