[Stephane]

Hi Mick,

My understanding is that dark frames depend on temperature, ISO, and exposure time. So unless all those conditions are the same, you will need to take separate darks on separate nights (you can get away with temperature +/- a few degrees). Bias frames are shortest exposure and do not depend on temperature, but do depend on your ISO. So if you change ISO, you will need new bias frames. Flat frames depend on focus and dust on your lenses. Since focus will change from night to night, in theory you would need to take new flats for every session, but in practice, I don’t and old flat frames work well, as long as they are not so old that new dust has deposited that is not being subtracted if I use the old flats.

If you calibrate all your sets of lights first with their respective calibration frames, you can then stack everything together without worrying. However, if you are using Deep Sky Stacker, or some other application which calibrates and stacks in one click of a button, you will need to make use of the “groups” at the bottom where you can put all lights, darks, flats and bias for each separate night in a separate tab.

Hope that helps and makes sense. I’m looking forward to reading other comments on this post as I too am still learning about calibration frames.

Clear skies,
Stéphane