ABSTRACT
This chapter discusses the general image processing principles. Astrophotography is consistently more demanding in regard to image processing than conventional imaging and it requires extensive manipulation to create the final image. Image processing increases the visual appearance of noise in the darker areas and there are some very clever tools that reduce it. Astrophotographers use an array of tools for image processing. Calibration and stacking are best achieved with specialist programs. Image manipulation software includes dedicated programs (Maxim DL, Nebulosity, AstroArt and PixInsight are prime examples) as well as general purpose editing programs such as Photoshop, Affinity Photo and GIMP. As with any image, after the general processing, there are always a number of things to tidy up. This may be cropping off a bright star near the edge of an image, altering the aspect ratio to suit a particular purpose and fine-tuning the color balance, mid-band contrast and shadow levels.
