XEphem is an astronomy program that runs under UNIX. It uses a
X-Windows based graphical system to display star charts and other
astronomical information. "XEphem, the brainchild of programmer Elwood
Downey, is a star-charting, sky-simulating, ephemeris-generating
celestial virtuoso that can do just about everything that the usual
Windows and Macintosh star-charting software can do -- and sometimes
quite a bit more. And it's completely free. What's not to like?"