Free Software

Stellarium website (excellent, free, multi-platform sky simulator) A must have!

SkyChart (Cartes du Ciel) is available for Windows, Mac and Linux and allows you to plot sky charts.

NASA’s Eyes Experience Earth and our solar system, the universe and the spacecraft exploring them, with immersive apps for Mac, PC and mobile devices. Versions include Eyes on the Earth, Eyes on the Solar System and Eyes on Exoplanets.