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I used to use dark flats and subtract them making the master flat.
I talked to Don Goldman and he said he just subtracts a bias and does not do dark flats.
I then tried that and I noticed better results. My CDK17 and 16803 camera vignette quite a bit so good flats are essential. I got the best results this way.
My procedure (not saying its the best) is about 6 darks into a master (my cameras are very low noise anyway) some are made from more like 15 darks. Its hard to do more than that as 1x1 binned files are 32mb each and CCDstack fails at about 15.
I take 3 flats for each filter and use the default combine in CCDstack.
I have a separate bias. I think I can up the number in it. I think some I use are only 3 biases so I should see if more makes a meaningful improvement or not.
Dark subtraction importance probably varies with camera brands. Some are cleaner than others. We should start a thread posting examples of 10 minute darks to get an idea of which are the cleanest.
My FLI Microline 8300 is the cleanest camera I have used. Amazingly perfect at -40C.
Greg.
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