DeepSkyStacker - DeepSkyStacker is a freeware for astrophotographers that simplifies all the pre-processing steps of...
PixInsight - A powerful deep sky stacking application for astrophotography.
SAOImageDS9 - An image display and visualization tool for astronomical data
Siril - Siril is an astronomical image processing tool, able to convert, pre-process images, help aligning...
RegiStax - Photography, Astronomy, Image, and Astrophotography
Fitswork - Fitswork is a windows image processing program, mainly designed for astronomic purposes.