xephem

Interactive astronomical ephemeris program

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 Elwood Downey ecdowney@noao.edu August 1995