wmJupiter is a Window Maker applet which features the planet Jupiter. It allows you to keep track of the Great Red Spot and the current distance in astronomical units (AE). The four Gallileo moons (Io, Europa, Ganymede, and Calisto) are also displayed when they are near the planet.
Planets is a fun, interactive program for many-body gravity simulations. The emphasis is on play: it's easy to add in planets, zoom in and out, change the physical constants, save and load configurations, etc. It's designed to be easy enough for a kid to enjoy, but that hardly precludes adults.
Astro::DSS Module is an object orientated Perl module that provides an interface to both the first and second Digital Sky Surveys at the ESO-ECF online archive. While the first sky survey is 100% complete, the second survey covers 98% of the sky in Red, 45% of the sky in Blue, and 27% of the sky in Infra-red.
SaVi is satellite visualization software that lets you create, run, examine, and modify satellite orbits in two and three dimensions. Simulations of Iridium, Globalstar, Galileo, GPS, and other satellite constellations are included. SaVi requires Tcl and Tk on a system with Unix libraries. SaVi works well with the 3D renderer Geomview. Geomview is optional, though recommended for its 3D rendering capabilities.
The Astro::ADS module is an OO Perl interface to the Astrophysics Data System (ADS) abstract service. The ADS is a NASA-funded project whose main resource is an Abstract Service, which includes four sets of abstracts: astronomy and astrophysics, instrumentation, physics and geophysics, and Los Alamos preprint server.
libnova is a general purpose, double precision, celestial mechanics and astronomical calculation library. It can calculate aberration, nutation, apparent position, dynamical time, Julian day, precession, proper motion, sidereal time, solar coordinates (using VSOP87), coordinate transformations, planetary positions (Mercury - Neptune using VSOP87), planetary magnitude, illuminated disk and phase angle, lunar position (using ELP82), phase angle, elliptic motion of bodies (Asteroid + Comet positional and orbit data), asteroid + comet magnitudes, parabolic motion of bodies (comet positional data), orbit velocities and lengths, atmospheric refraction, rise/set/transit times, and semidiameters of the Sun, Moon, planets, and asteroids.
Nova is a free Integrated Observational Environment for astronomers. It combines Ephemeris functionality with the capability of controlling modern "goto" telescopes and popular CCD cameras. Nova combines image capture, telescope control and ephemeris functionality into a single application. The main goal of Nova is to make it easy(ish) to capture CCD images of objects with a good degree of accuracy. Nova is also able to manage several kinds of astronomical database (i.e GSC, USNO, SAO, etc.) and makes it easy to automatically schedule observational activity through the use of target object lists.