Being a Traveller RPG fan, as it was one of the first RPG's I was ever exposed to (the Traveller Book from 1982 was at my local library in the 90's), I couldn't resist getting into some of the other variations of the game that have since hit the market. Cepheus Engine, based on the Mongoose Traveller version, really caught my eye as it has OGL content available. Also, some of the best resources are made by Cepheus Engine game developers like Stellagama Publishing. Their Subsector and Sector maps are some of the nicest PDF files I've found to work with.
Being such clear files, I imported one into GIMP (free open source raster graphics editor) to create the above sub-sector (parts of it pictured). Took me a while, as I created some of the symbols in Inkscape (free open source vector graphics editor) and then exported them as .png file that contained a transparent background. Then it was just select, copy/paste, and scale where required.
Anyone with experience using GIMP or Photoshop should have no issues using such a file to fill out a blank subsector they roll up!