Astrophotography by Dennis Friedman

Standard calibration requires multiple dark frames (again at least five), flat frames (fifteen or more), and flat dark frames (fifteen or more). 

The flats can be taken at an exposure length from 2 to ten seconds. 

Flat Darks are taken with the lightbox off but same integration times. Images processed with standard calibration have bias level correction, dark current correction, hot pixels removed and no vignetting. 

Integration time of these frames must be the same length of time as the raw exposure. 

The Flat frames will aid in reducing or eliminating those nasty dust donuts.