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Pete,
Try this..ensure the CCD temperature is the same, then
1. take 2 "bias" frames
2. Take 2 dark frames of ideintical duration (say 10 minutes each).
Subtract the 2 bias frames and measure the noise.
Convert to actual noise, i.e N(bias) = G x measurement / sqrt (2).
Subtract the 2 dark frames, measure the noise and similiarly convert to real dark noise, i.e N(dark) = G x measurement / sqrt (2).
From SBIG website G (or Gain) = 0.37 e- / ADU
Then
Dark signal = N(dark) ^ 2 - N(bias) ^ 2
Dark Current = Dark signal / exposure
See what you get.
Terry
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