From SBIG manuals:
  • During readout of a pixel, the charge in a pixel is stored in a capacitor temporarily. After readout, the capacitor is drained and the next pixel charge is stored there, however, some residual charge remains, which will effect the next reading, contributing to (the apparently dominant source of) noise.
  • For images taken with exposures of more than 1 minute, the later subtraction of a dark frame taken at the same exposure and temperature can result in a large reduction of over-bright pixels (important for looking at star fields).
  • Vignetting and non uniform pixel responsivity can be removed using a flat field image, an image taken of a uniform source. Little visual difference in images for a system with little vignetting, but recommended for accurate photometry measurements.
  • Noise due to dark current defined as the square root of the number of electrons accumulated during integration time. Supposedly every 5-6 degrees of temperature reduction reduces the dark current by half.
-- DavidHadden - 20 Oct 2015
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Topic revision: r1 - 20 Oct 2015 - DavidHadden

 
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