Data Processing
Depending on the CCD sensor - lens combination used, few 10s to 100s of stars are captured with a single digital zenith image. The positions of imaged stars are measured by means of digital image processing algorithms, such as image moment analysis or point spread functions to fit the star images. Star catalogues, such as Tycho-2 or UCAC-3 are used as celestial reference to reduce the star images. The zenith point is interpolated into the field of imaged stars, and corrected for the exposure time and (small) tilt of the telescope axis to yield the direction of the plumb line.
Read more about this topic: Zenith Camera
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