Build your own GPS unit
ESP32 mySQM+ Sky-Meter/Weather Station with loads of features
Earth orbits and satellite coverage display in 3D on your laptop.
Pikon-Stelarium interface to use with azimuthal mount
C API to control NexStar compatible telescopes
Cross platform Perl API to control NexStar compatible telescopes
Open PECTool - manipulate peroidic error data for Celestron mounts.