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Old 29-05-2016, 10:18 AM
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Shiraz (Ray)
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Join Date: Apr 2010
Location: ardrossan south australia
Posts: 4,821
While waiting patiently for Australia post to move my camera from NSW to SA, have been analysing some dark image data presented on CN to try to understand the "amp glo" that some users are reporting. I had to make a few assumptions about how the camera and software works, but if I got anywhere near right, the glow is just slight variation in dark current across the chip (due either to peltier temperature variations or to the chip itself).

my best guess is that, at the tested -15C, the dark current varies (over the specific chip where data was available) from about 0.013 e/s/pix in the centre to 0.021 in the brightest of the "glow" on one edge. This level of dark current is not as good as the Sony CCDs, but slightly better than the Kodak ones - ie neither the dark current nor noise from the "glow' should be a major issue. However, there may possibly be some difficulty with scaling darks, if the start point varies with position on the chip. Real darks taken at the true temperature may possibly be best with this camera. Of course, the dark current is still very low and it may be possible to get good results by ignoring dark calibration altogether and relying on dithering. That could be very useful if the datasets get big (eg with short subs)

Last edited by Shiraz; 29-05-2016 at 11:02 AM.
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