Nightshade is free, open source astronomy simulation and visualization software for teaching and exploring astronomy, Earth science, and related topics. Nightshade is a fork of the award-winning Stellarium software, but tailored for planetarium and educator use.
The emphasis is on usability
... [More], realism, feature stability, and performance. It is backward compatible with scripts for Stellarium 0.8.2 and earlier using the StratoScriptTM language developed and maintained by Digitalis Education Solutions, Inc.
It is available for Linux, Windows, Mac OSX, and other platforms. [Less]
kepler is a library of C routines for astronomical calculations. It features the following:
* The entire VSOP87 theory for calculating the positions of the eight planets.
* The entire ELP 2000-82B theory for calculating the position of the Moon.
* An analytical theory for calculating Pluto's
... [More] position for the period 1700AD-2100AD.
* The ability to convert osculating orbital elements to heliocentric coordinates.
* The latest IAU 2006 precession and IAU 2000A nutation models.
* Routines for calculating sidereal time using the current IAU resolutions.
* An implementation of the Ron/Vondrak theory of annual aberration.
* Routines for Julian date calculations.
* Routines for coordinate transformations, rotations and parallax corrections. [Less]