Tenmon – FITS and XISF image viewer, converter and indexer

It is intended primarily for viewing astro photos and images. It supports the following formats:

FITS 8, 16 bit integer and 32 bit float
XISF 8, 16 bit integer and 32 bit float
RAW CR2, CR3, DNG, NEF
JPEG, PNG, BMP, GIF, PBM, PGM, PPM and SVG images

Features:

Using same stretch function as PixInsight
OpenGL accelerated drawing
Index and search FITS XISF header data
Quick mark images and then copy/move marked files
Convert FITS <-> XISF
Convert FITS/XISF -> JPEG/PNG
Image statistics mean, media, min, max
Support for WCS
Thumbnails
Convert CFA images to colour – debayer
Color space aware
Batch processing with JavaScript
Thumbnail generation for FITS/XISF images in Windows File Explorer

You can download source code or pre-build binaries for Windows and MacOS here
On Linux you can install flatpak from flathub.org by running this command
flatpak install flathub space.nouspiro.tenmon