kete
This is very niche, only for people who do astrophotography or astronomers, mostly because of the required specialized file format. I have slowly built out a set of tools for asteroid orbits and photometry (measuring how bright stars/asteroids are). It is very rough still (Desktop only), and it only supports the FITs file standard. https://www.astrometry.space/ Basically it is a full professional grade telescope processing pipeline in your browser. It does 2 queries to some custom databases to identify known asteroids and stars, but all image processing and calculations are done in the browser. This means the backend is pretty tiny. That said it is running on an old box in my closet, so queries may take a while if it gets hammered. I built it since I have worked with quite a few astronomers over the past 4 years and I keep watching them do the same steps, purely built to make my friends lives easier. I wrote it all in rust and managed to compile it into wasm. With some help from fable as I am not a frontend guy at all, I built it into a small website. Some of the code is public, the orbital mechanics code I wrote while I worked at Caltech. Which is being used on SphereX, NEO Surveyor, and the Roman telescopes to identify known asteroids. https://github.com/dahlend/kete