I have an anomaly I'm trying to figure out with my ASI6200MM I haven't seen before. I imaged the same target for four nights in a row, same settings with similar 4 day stretch of sky conditions using ASIAir. However the second night, as can be seen in the graphs from PixInsight SubframeSelector, the noise is much higher and there are numerous saturated stars. This can also be seen in the unstretched subs from first and second night posted below.
It's as if the gain is increased on the second night, however the gain is set to 100 for all four nights and the exposure the same at 180s. This is also verified in the FITS headers. Sky conditions couldn't explain this as all nights were clear with about the same transparency, and both noise and star saturation increased greatly for just second night imaging.
Could there be a bug in ASIAir not setting the camera gain correctly the second night? I can't think of another reason that would cause this, but I could be missing something. Download sample FITS from first and second night here: https://www.dropbox.com/scl/fo/8h5s0jotwr24d8izqe0x4/AHWf1AB4c5nOTbNI8812Pcc?rlkey=krqal5ws0hgkeooecqe3o6mcc&st=c3g6ez71&dl=0
