https://www.linuxlinks.com/tenmon-fits-xisf-image-viewer-converter-indexer/
Tenmon is a FITS and XISF image viewer, converter and indexer - LinuxLinks
Apr 23, 2025 - Tenmon is a FITS/XISF image viewer with multithreaded image loading. It's written in C++ and published under the GPL.
is aimage viewerfits