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Hey Rick,
Can I ask what Exposure times you were using for your darks to derive your dark current? Did you try several exposure lengths? And if you did, was the e-/sec the same for all exposures?
What I'm seeing in my data is a *fairly linear relationship between dark current and exposure length, but when I try to compare apples with apples by figuring out the actual e-/sec by dividing by exposure time, I get the dark current decreasing rapidly from 0.0274 e-/sec to a base of around 0.0096 e-/sec at Gain 139 (which is not too different from your data).
Once converted to e-/sec, shouldn't you get basically the same numbers for all sub lengths?
I can't think of kind of noise that *reduces rapidly as exposure increases. Usually it's the other way round.
That means without taking the sub-length into account my estimation of Dark Current may be out by as much as 186%.
I can only think of some residual thermal activity from the preceding sensor read.
I may try another series, leaving 10 minutes between reads to see if that is the issue.
It doesn't stop me imaging, of course. It just means that there is another variable to consider for determining optimum exposures, I guess. I'll also have to be very careful to get darks that are the exact same length as the subs (no scaling during calibration).
Cheers
Markus
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