SCRUBBING DATA by Ron Brecher Demystifying Image Calibration This important step will dramatically improve your imaging results. All deep-sky astrophotography requires some form of image calibration to remove unwanted signal. This deep photograph of the entire Veil Nebula supernova remnant in Cygnus consists of more than 17 hours of exposures through color and narrowband filters calibrated with flat-field and dark exposures. 36 N OV E M B E R 2 019 * SK Y & TELESCOPE