Bias MAD ASI1600MM

[alphascorpi]

I have shoot a serie of bias frames with my asi1600mm-c.
Gain: 0, Temp.: -10°C
Goal: Is there a function "Bias quality versus time"?
Time: 0.05 / 0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 / 0.7 sec

Result: with 0.2 and 0.3 second (most recommended for asi1600mm-c) I get a MAD of ZERO! All other cases gives MAD 16.
The MAD 0 images look very soft

My question:
A MAD of ZERO is theoretical possible, but in the practice?
If I increase the temperature to 10°C the MAD is overall 16.

Should I take the bias with MAD = 0 or is this parameter in this case useless?

Thanks for your help, Ed

[Juan Conejero]

Hi Ed,

If MAD is zero, then more than a 50% of the pixels in the bias frame have the same value. This is strange in my opinion, since one would expect more pixel-to-pixel variations in a bias frame. Such a large amount of identical pixel values sounds like some required threshold has not been reached. Of course I may be wrong, since this is what you get with recommended exposure times...