Photometric Calibration of UVIT

Photometric calibrations are essential for accurately determining the photometric magnitudes of celestial objects. This thesis focuses on the calibration procedures for the Ultraviolet Imaging Telescope (UVIT) onboard ASTROSAT. The aim is to obtain precise estimates of the photon counts per second (C/S) in UVIT filters for calibration sources, including the white dwarf HZ4 and the open cluster NGC188. The procedures involve correcting for instrumental effects such as saturation and spatial variation of sensitivity. Emphasis is placed on evaluating the effectiveness of flat field correction techniques in minimizing spatial variations, ultimately leading to improved photometry.