XEphem is an interactive astronomical ephemeris program for X Windows systems. It computes heliocentric, geocentric and topocentric information for fixed celestial objects and objects in heliocentric and geocentric {orbits;} has built-in support for all planet {positions;} the moons of Jupiter, Saturn and {Earth;} Mars' and Jupiter's central meridian {longitude;} Saturn's {rings;} and Jupiter's Great Red Spot

WWW: https://xephem.github.io/XEphem/Site
