Hallo,
while trying to use an asi178mc with a raspberry pi as an allsky camera, I notices brightness "steps" when increasing the exposure time.
As shown below, this means the average and median brightness of an (day time, raw 16, snapshot mode) image stays constant for an interval of 40µs.
This is also visible on the pixel level:
The camera is controlled with https://github.com/python-zwoasi/python-zwoasi. The full code can be found at https://github.com/GermanHydrogen/pyobs-asi/tree/test. The short version of the settings is:
gain = 1
gamma = 50
brightness = 0
One post (https://bbs.astronomy-imaging-camera.com/d/10151-minimum-exposure-time-asi178mc) does mention similar behaviour, with the problem being, that the pi defaulted to a usb 2 connection.
In my case, the raspberry pi at least reports via lsusb -t
, that the camera uses the full usb 3 connection speed.
At the moment, I'm out of ideas how to explain or fix this behaviour.
Best regards,
Wasserstoff