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Telescopes usually do not illuminate the detector homogeneously. Moreover, dust on optical surfaces and sensor lead to | Telescopes usually do not illuminate the detector homogeneously. Moreover, dust on optical surfaces and sensor lead to darker patterns on resulting image, and the sensor itself has a different response to the number of photons hitting different photosites. To correct these effects one need to divide each light images by the master flat, which should be the median of single exposures of a homogeneously and non-saturating illuminated area. | ||
Latest revision as of 12:27, 11 April 2016
Flat
Telescopes usually do not illuminate the detector homogeneously. Moreover, dust on optical surfaces and sensor lead to darker patterns on resulting image, and the sensor itself has a different response to the number of photons hitting different photosites. To correct these effects one need to divide each light images by the master flat, which should be the median of single exposures of a homogeneously and non-saturating illuminated area.