Stellarium
Desktop planetarium.
Quoted from: http://www.stellarium.org

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Stellarium is an open source desktop planetarium. It renders the skies in realtime using OpenGL, which means the skies will look exactly like what you see with your eyes, binoculars, or a small telescope. Stellarium is very simple to use, which is one of its biggest advantages: it can easily be used by beginners.

Click Image To Enlarge
Screenshots Download
Stellarium is an open source desktop planetarium. It renders the skies in realtime using OpenGL, which means the skies will look exactly like what you see with your eyes, binoculars, or a small telescope. Stellarium is very simple to use, which is one of its biggest advantages: it can easily be used by beginners.
Features
sky
- over 120,000 stars from the Hipparcos catalogue with info
- asterisms and illustrations of the constellations
- images of nebulae
- realistic Milky Way
- very realistic atmosphere, sunrise and sunset
- the planets and their satellites
interface
- a powerful zoom
- time control
- multilingual interface
- scripting to record and play your own shows
- fisheye projection for planetarium domes
- spheric mirror projection for your own dome
- graphical interface and extensive keyboard control
visualisation
- equatorial and azimuthal grids
- star twinkling
- shooting stars
- eclipse simulation
- skinnable landscapes, now with spheric panorama projection
customisability
- add your own deep sky objects, landscapes, constellation images, scripts...
