ABSTRACT
The calibration process measures the consistent errors in an image and removes their effect. These errors are corrected by subtracting an offset and adjusting the gain for each image exposure. Bad pixel mapping is not an averaging technique per se, but is used to substitute hot pixels in an image with an average of the surrounding pixels. It is an alternative to calibrating light frames by dark frame subtraction. Image stacking is essentially two activities: registration and integration. Although a few images can be registered and blended in Photoshop, astrophotography demands advanced tools for accurate registration and statistical combination. Capture programs such as Maxim DL and Sequence Generator Pro usefully label each file with essential exposure about the exposure conditions and equipment. These "tags" enable programs such as Maxim DL and PixInsight to segregate files by exposure length, binning and filter type.
