dbradf Am I missing something?
Flat frames are used to correct for properties of the OTA and optical train, and has nothing to do with the camera sensor . You do not need to use the same gain when you take a flat frame to match the light frames, nor at the same temperature. The sensor errors for the flat frames are taken care of by taking flat-dark frames.
Am I correct in setting the fixed gain?
If your camera is not stable (the ASI294 is one of the worst), do some experiments yourself to find a "best" set of parameters (gain, temperature, etc) to take flats with. You can choose very different parameters to take flat frames than the ones you use to take your light frames.
And then take flat-darks (sometimes called dark-flats) after taking the flat frames -- these are used to correct for camera sensor errors in the flat frames -- the flat-darks should be taken at the same temperature, gain, offset, exposure time, etc as your flat frames. The only difference is that the flats are taken with illumination, while the flat darks are taken in darkness. Make a master flat from these flat and flat dark frames.
Chen
