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Old 29-01-2014, 11:09 AM
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Shiraz (Ray)
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Join Date: Apr 2010
Location: ardrossan south australia
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very informative thread - thanks guys.

Presumably bias drift will vary with camera design. For interest, I looked up the recommended support circuitry for a couple of popular CCD chips - one manufacturer suggested what appears to be a thermally compensated output buffer, the other a straight emitter follower, with no compensation. One would likely drift only a little bit, the other probably more so.

It might be informative to have a more complete list of cameras that could benefit from overscan compensation. Will do a few tests on the H694 bias stability and post here - it doesn't produce overscan data as is, but I am not sure how much it drifts.

As I understand it, once you have reliable set of darks (for which you might need overscan compensation), the issue is dealt with - all you need overscan for is to get the right dark current to scale and subtract. Bias drift in the lights will only show up as a variable offset, which can be easily dealt with - is this a reasonable statement? EDIT: of course this only applies to pretty pictures, not science data - overscan compensation would be essential for some forms of photometry.

regards Ray

Last edited by Shiraz; 29-01-2014 at 09:28 PM.
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