I am using an ASI 183 for deep sky photography.
Working with the RASA I normally take 120 seconds (or at most 180 seconds) subframes with unity gain (117) and -10°C temp.
I recently shot the orion nebula, so I tried to configure gain 0 and 20 second exposure.
The problem is that every single subframe shows horizontal bands (it had never happened to me before).
I can't remove the bands either with dithering or with bias frames.
Do you have any advice?