ALFOSC Bias frame, Ampl A, high gainThe vertical gradient in short exposures is typically a few ADUs. In long exposures it can be tens of ADUs, however the overscan follows the trend, hence this can be subtracted straightforwardly (see the CCD#8 pre-commissioning report).
 An average of columns 900 to 1200 of a combination of ten bias frames. Click here to see large image.
 A combined frame of ten bias frames. The grayscale cuts are +/- 3 ADUs. Click here to see large image. Note that the pre- and overscan regions are nearly invisible in the grayscale image.
|