Hi all,
Last night I got the chance to test new ASI178MCC and noticed strange issue with bias frames.
I used ASCOM drivers 1.0.2.22 and SIPS for capture, and tried capture some dark and bias frames
with following params:
GAIN used : 0, 50
Offset used: 50, 100
USB speed: 40
All frames captured @-10C
I consistently get higher mean pixel value in short exposures, for example Bias frames with offset 100, gain 0 give me mean pixel value of 408.3 most of the time, except sometimes mean jumps to 410.8 - for 10 frames will have main pixel value around 408.3/408.4 and then suddenly jumps to 410.8 for couple of frames and then returns to 408.3.
2 minute exposures are far more consistent - but give me mean pixel value of 399.4 - lower than bias frames! (they should be a bit higher - depending on dark current).
So when I create master dark frame - it has negative mean value! (~ -8).
I suspect that there is some internal calibration - can this be switched off? Or at least can bias frames be stabilized (so that their mean value between frames does not jump between 408.3 and 410.8 in this case). Does anybody know what is actually being done to frames in sensor and in drivers (so I can try to devise proper calibration procedure).
@Sam
If drivers are doing something internally to reduce some kind of artifacts in frames - could we please have some kind of switch in drivers so we can turn off internal optimization / calibration?
I would really like to have proper frames in order to perform my own calibration and have a chance of using for example dark optimization (for this I need pure dark signal without any DC offset introduced).
