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Now, I do take bias frames and subtract them from my darks. I do this so that the darks are scaleable.
My theory is that I only need one darkframe for each bin level, this is what CCDStack is telling me. So I have one 30minute darkframe for 1x1 and 2x2 at -15C. I can go down further in temperature in winter, by not in summer, the darks subtract out nicely so I like to keep one temperature. Apparently when the darks are made in this manner they are scaleable for both time and temperature.
I assume that what CCStack is doing is subtracting the bias from the dark so that what you're left with is "pure" dark noise. As the bias doesn't change in intensity over time, but the dark does, it scales the dark then adds the bias to the dark before subtracting. Put another way the scaled dark has lost the bias information (as it has been subtracted in the master making process), so it has to be subtracted as well as the dar from the light.
Does this make any sense?
Oh BTW Paul, welcome to deep sky imaging with a dedicated CCD. I look forward to your results, the camera looks like a cracker!
Cheers
Stuart
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