Quote:
Originally Posted by roughy
Is there a formula for calculating the integration time for a flat based on your chip and camera characteristics? I have been perusing the "Handbook of Astronomical Image Processing" but cannot seem to find a specific equation.
Cheers
Mark
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There's a fair bit of data about this. Richard Crisp wrote a paper about this 4 months or so ago. You could google for it.
I generally shoot until I get about 20,000 ADU. His paper suggests to do more as CCD responses are linear.
On the other hand I have had flats that are too bright cause unwanted effects in my images. Not 100% sure why. So I tend to stick to around 20,000 ADU plus or minus a bit. I also take a dark and subtract it when doing the master dark.
Also using good exposure darks helps with the flat fielding. A poor dark seems to throw off the flat fielding as well.
Greg.