Light pollution adjusted dark frames?

[Dave Lloyd]

This is probably crazy. Why can't dark frames for stacking be calibrated to account for light pollution. I don't mean a succession of ever darker t shirts over the lens but an adjustment to the darks in d.s.s etc.This would ascribe a value corresponding to the ambient light which could then be cancelled out. Totally bonkers?

[D4N]

I think you would run into problems with that. LP is a gradient and as your target moves across the sky the amount of LP will change. As such it is better to stack it and then post process it out rather than try and pre process it out.

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[Dave Lloyd]

Ah, good point. Thanks for that.

[dph1nm]

Actually what you can do is take a series of light frames offset from your target and median them together to remove the stars. This then acts as a 'master sky frame', which you can subtract off (it also contains the dark as a bonus). Although this is probably the best way of  creating a flat background, it has the disadvantage of wasting a lot of precious observing time!

NigelM

[Dave Lloyd]

Yes I see what you mean. Perhaps you could save a set of different conditions to use as masters. As you say though this would be very time consuming.