Gain and Offset settings for ASI585MC Pro

So M13 was pretty bright, 120second exposure was resulting in a completely white photo.

I went with 30second exposures with this target:

https://www.astrobin.com/0b7nec/



I guess the question is now, do I stick with very short exposures, or lower the gain?
Will changing the offset help?

Lowering the gain *does* reduce star saturation because the same number of electrons collected (i.e. the same amount of light) will result in a lower value read by the pixel. Saturation is simply the value hitting the maximum, so anything that makes it more difficult to achieve the maximum helps with saturation. Of course fainter signal suffers and read noise becomes more significant, otherwise we would be using only gain 0. It's a trade off. 

Based on the manufacturer's diagrams, lowering gain below 100 will give you better dynamic range than gain 252. And you will need 5 times as many electrons to reach the same signal intensity, which is important if your stars are blown. 

However, it would be a good idea first  to make sure your stars are indeed saturated, because 30 seconds seems like awfully short time to manage and clip the tiny stars in the outskirts of M13. Maybe it is just your processing, especially BlurX if it is too aggressive, and of course the stretching done. Try reading out a few pixels on stars in the (unstretched) image after background removal. Does it say 65535 or whatever the maximum value is? If not, then they are not saturated. Proceed to stretching with MaskedStretch, leaving everything to default. You should be able to discern two star populations (blue and yellow). That's what you are aiming for, in the main. 

Cheers,
Dimitris

Mateusz Bogucki:
Hey, has anyone figured out which offset is best for this camera? 

Best,
Mateusz