JasonMathias fastest shutter speed possible on ASIStudio for taking bias frames?
The point of the bias frames is to take a frame that does not include dark current noise. As a simple explanation, think of a dark frame as the sum of a DC bias plus a bipolar noise term.
The DC bias is needed to keep the noise term bipolar, since the camera sensor reads intensity (electrophoton counts), and not signed voltages.
If you don't remove the DC bias, then you cannot scale the dark current, and you cannot stack the dark frames either (since you will be accumulating the DC bias). So you take short exposures, and use them to remove that DC term.
As such, a few order of magnitudes shorter exposure than your dark frame is more than sufficiently accurate. Most people just set it to the fastest exposure available, so no thinking is involved (unfortunately, they also don't understand the actual arithmetic behind the bias frames).
Chen
