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Dark and flat capture bias frame issue
Posted: Sat Oct 26, 2019 10:58 am
by TheAmateur
When capturing darks and flats, the bias frame capture appears to use a fixed value of 1ms exposure time, not the fastest available shutter speed (e.g. 0.1ms or below for ASI183mm).
Re: Dark and flat capture bias frame issue
Posted: Sat Oct 26, 2019 8:11 pm
by admin
Hi,
Some models of camera have a tendency to misbehave at very short exposures even though they claim to be able to carry them out, so I didn't want to take the bias frame which is automated down to the very shortest exposure levels.
The actual length of the bias frame exposure doesn't really affect the results as long as it is considerably less than the flat frame exposure time. For instance if you are taking flats with a one second exposure then you could get perfectly good results by subtracting 100 ms exposure bias frames from them. If you were to perform this measurement you would end up with data that indicated the brightness level created by adding 900 ms of exposure without any pedestal level which is exactly what you need in a flat frame.
Cheers, Robin