Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
PixInsight - A powerful deep sky stacking application for astrophotography.
GIMP - GIMP is a multiplatform photo manipulation tool.
Siril - Siril is an astronomical image processing tool, able to convert, pre-process images, help aligning...
Affinity Photo - Affinity is the imaging and design suite for creative professionals exclusively for Mac.
APT (Astro Photography Tool) - APT stands for "AstroPhotography Tool" and it is like Swiss army knife for your astro imaging sessions.