Weird histogram with QHY268M

[Fukinagashi]

I got several pictures of C2022 E3 with Sharpcap in LRGB but I see a strange histogram very shifted toward blacks (see pic) while the histogram of the corresponding dark (same exposure, same gain, same offset, same binning, same readout mode, same temperature), taken with a different software, looks very different, this leading to an improper calibration.
Any idea?

[admin]

Hi,

do you have the 'capturesettings.txt' files that SharpCap saved next to the images? Those record all the camera settings that you used when capturing, and I suspect will contain the answer to this mystery. The two things that come to mind are

* what offset value did you set in SharpCap
* were you using dark correction in SharpCap, therefore the saved frames are already subtracted?

cheers,

Robin

[Fukinagashi]

I used 25 as offset value, the same used for darks.
I did never took a dark frame with SharpCap, so automatic dark subtraction should be off.
Attached the Settings.txt file.
Thanks for help.

[admin]

Hi,

yes, no dark subtraction or background removal or similar there. Some things to check though to see if they might be causing it

1) Read mode : Photographic DSO - perhaps other read modes behave more normally
2) Brightness/Contrast/Gamma - I think the settings you have are default and fine, but not 100% sure - worth checking

I can't see anything else though

cheers,

Robin

[Fukinagashi]

Then could the camera be defective?
Is there any test (in SharpCap) I can do to verify that it's working properly?

[admin]

You could try running the SharpCap sensor analysis and comparing the results you get at the end with other people's (and the manufacturers) quoted figures for read noise, etc. That gives the camera a good workout (lots of different gains, exposures, offsets, etc).

cheers,

Robin