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I once saw these on images calibrated with Dark Frames from our SBIG ST7 and figured that if hot pixels are white, then cold pixels must be dark as they would be less sensitive to the incoming photons. I was able to remove them (automatically) using the “Remove Cold Pixels” function in CCDSoft.
However, I was very surprised to find these in the (cooled) Dark Frame as the ST7 is temperature regulated. The repair operation reported back that it had repaired a number that was well over 100 from memory.
Looking at your example, you seem to have 100’s – I wonder if this indicates something going wrong with the calibration routine?
Does Images Plus have a cold pixel repair tool?
Incidentally, your 300 second Darks look significantly less noisy that those from the ST7, even when it is cooled to 25 deg C below ambient!
Cheers
Dennis
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