Perhaps it's already possible and I have something misconfigured but when I double click in macOS's Finder on a .fits file then KStars itself opens (configured that well) but doesn't open the FITS viewer with the selected file. Would that be possible to configure/setup?
Thanks for the great work and port (Stephane Lucas) to macOS!
AFAIK, this is working on Linux so for MacOS/Windows, KStars should register with which meta type it can read/open... though even in Linux it will always start a new process now whenever you click on a FITS file instead of re-using the existing process.
While this might not be helpful in solving this particular issue with opening the images in the KStars preview window, the solution I use is Observatory for the Mac. codeobsession.com
It installs a fits/xisf plugin for preview functionality in the finder. So not only will it turn your image thumbnails into images, but you can also press the spacebar to preview the image in a large window.
There are now multiple programs that will quick look fits files in the Finder. Some are even free, and do FITS and XISF. They're in the Mac App Store. Still does not resolve the issue of opening them into the Fits Preview of KStars. But I wonder if the Fits Preview could be released as a standalone app on the Mac?
In addition to what you said.....
I tried to add Kstars using the Open with dialogue, but even after I do that it doesnt seem to open the FITS viewer within Kstars. Just ends up opening Kstars and displays the sky chart
Celestron Astromaster 130 on HEQ5 Pro mount, ZWO ASI224mc, 30mm guidescope with ASI120mm mini. All managed using Kstars/Ekos on RPi with Astroberry build.
I see that the below command line works fine:
It opens up KStar with the image shown.
Releasing a separate version of KStars just to get this to work seems silly
On macOS the opening of files is related to the UTI of the file according to: en.wikipedia.org/wiki/Uniform_Type_Identifier#Looking_up_a_UTI
Below you can see that a file saved by KStars differs in the UTI from a file that is saved by another program: Siril. Note that the file name extensions also differ by the extra s in .fits in KStars vs .fit in Siril. Both are "FITS file" though.