Thank you for your reply.
Yes, in post #4 of this thread I confirmed already that my problem with the bit depth setting (8 / 16 bit images) is solved and that it was caused by PHD's New Profile Wizard.
However, there are other issues that are caused by the camera or the camera driver:
Item 1:
The direct camera driver discloses that offset can be set in the range of 0 to 1200. I tried some values and captured some dark frames. The images always looked the same visually and there were no differences in the histograms. The FITS header says: offset = 200 in all cases. This is indepedent of which camera driver (ASCOM or direct) is used. Apparently the offset is not variable at all, is it?
At gain = 350, the signal is clipped severely (13 % at a temperature of 19 °C). I will never use a gain > 250, so this is no issue for me, but I would like to have the possibility to set a lower offset. With the fixed gain of 200, the following values resulted in 2-s dark frames:
gain median stdDev
110 3120 36.6
150 3024 59.0
200 2864 97.2
250 2544 158.7
So there is plenty of room for using offset values lower than 200. This would result in higher dynamic range of subframes.
Then I varied gain in the range of 0 to 350 and captured dark frames.
Item 2:
As expected The distance of peaks in the histogram is 16 ADU at a range of 0 to 65535 ADU, corresponding to a sampling of 12 bit for gain values of 0 to 99. However, starting from a gain value of 100, this distance is 32 ADU, corresponding to a sampling of only 11 bit. Why is it so?
Item 3:
The switch from LCG to HCG occurs at gain = 107, and not at gain = 106 as described in https://www.zwoastro.com/product/zwo-asi220mm-minimono/ in the read noise graph. Please correct the documentation.
Bernd
