I was wondering how people generated star maps/galactic maps for their world, I've been struggling to find any tools.
When I needed a map (for a game though) I wrote a little program that, based on a seed and some coordinates, generated me star systems on a grid. It would take in the seed as well as x,y,z coords and then generate a new system seed from that.
The grid size I choose was 1parsec³. Then some research on wikipedia on star density within our galaxy and based on that the chance for a star system with that cube.
Then I would also generate some planets orbiting the star(s). As for the star itself, I had a possibility for 1-4 stars in a system I think.
For each planet/star/astroid you can generate an id from 0 (star) to i (your last object) and generate new seeds.
This way you have a hand written seed from the beginning that generates more "random" numbers you can base further generation on. But since your seed + the coordinates form a grid cube seed and these create the next and so on you can with a single seed generate a universe that's always the same. It is also "endless" (until you get floating point or max int problems). You could also generate a very specifc zone of it on demand if you know the coords.
This way you can create an endless universe to use for whatever purpose. It's mostly data though and quite hard to make it into a human readable map. More of a "play area".
I for example like to use it as base for ideas. You could say "I live in cluster 000x000y000z and go 200 clusters on the x axis to 200x000y000z" and the program tells you:
You find a binary star system with 4 additional planets.
Now you can base your story on that area. ;)
Should you want to use this as a basis for say a game or an interactive application it's nice to note, that you have to store the inital seed and nothing else, if you generate all information from it.
Textures as well as heightmaps can be generated from this too with fractal brownian motion or simplex noise/perlin noise. This might or might not be very useful depending on your case though.