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Re: (ATMoB:Discuss) astrophotography with ordinary digital cameras
on 2001/12/04 16:49, Bruce Berger at berger ^a^ mediaone dawt net wrote:
> Couldn't one just capture one dark frame at the start of shooting and use it
> throughout the night? Or is it desirable to have the dark frame taken when
> the CCD is close to the same temp as when the subject photo was taken?
>
> Bruce Berger
The problem is that even in the dark frame there is some randomness. Most
ccders take several dark frames and average them, or take one very long dark
frame and divide the pixel values by an appropriate number to match the
image exposure. Another problem is that a photo-style is not going to be
held at a constant temperature; the changing ambient temperature will
continually change the chip's temperature. So a dark frame taken up front
will only be useful for as long as the temperature of the chip remains the
same as the when the dark frame was taken.
-lou
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