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]