Orrery

"Orrery" is an orbital-motion visualisation application. Orrery shows the sun and planets, minor planets, our moon, stars and earth satellites. It uses an intuitive graphical interface to display orbital motion, for both planetary astronomy and satellite dynamics. It is designed from the ground up as a tool for educators in astronomy, but may also be used to determine visibility, look angles, and ground tracks. Orrery allows both plane projections and perspective views, with either user-selected view angles or automatic tracking. Orrery comes with instructions in HTML format. System requirements: * Macintosh System 7.1 * At least 3.0 Mb of available RAM * 1.4 Mb of hard drive space Orrery is $5 (US or Cdn) shareware. John D. de Boer deboer@king.igs.net