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The Ultraviolet Imaging Telescope (UIT) detectors include solar-blind image tubes which introduce small but significant geometrical distortions to the data. These distortions, which are as large as 20-30 arcseconds at the field edges, are corrected to 2-3 arcseconds, approximately the resolution of the images, by the procedure described here. We first measure the distortion through comparison of UIT images to digitized Palomar Guidestar survey plates, modeling the distortion with a 3rd-order polynomial fit. The model is used to improve computed astrometric plate solutions. It is also used to remove the geometric distortion while transforming the image into a standard north-up, east-left orientation.
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