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Old 09-04-2010, 11:56 PM
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Exfso (Peter)
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Join Date: Sep 2006
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This is a brief description of what flat frames are all about.

Flat frames are essential if the faintest parts of a target are to be detected. The basic concept is to point the system to a uniformly illuminated light source and take an exposure. The resultant exposure will capture all of the imperfections in the system - vignetting, dust on the optical surfaces, off-axis optics and other disturbances.

The imperfections etc are then removed in stacking the flats with the other frames. A pretty rough explanation but I think you should get the general gist.

Some people use a white T shirt the next day to achieve this, but it has its limitations. It is much better to take the flats at the same time as the primary image as nothing in the image train should be changed before taking flats. You can then move onto the next image, move your focuser etc without hassles as you already have flats prepared for that particular image.
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