Celestia

Here is one of the most wonderful software provided by the Open Source community! To find out what’s wonderful about it, simply click on "screenshot" at the bottom of the page and you will discover some of its graphic qualities.

Celestia is a 3-D space simulator designed to travel through the universe and explore planets and stars. When science merges with poetry!

It’s an ambitious project, concentrating many scientific and human resources. And the result is worth because, as some expert users say, it’s one of the richest softwares in this category.

About add-ons:
An add-on is a piece of code added by external programmers to improve the software. Celestia add-ons are multiples, and provide hypothetic worlds, spacecrafts, additional planet rings or moons, high resolution pictures, etc. Add-ons are generally distributed in a zip file with their original path. So, to install it, simply unzip the pack where Celestia is located (c:\Program Files\celestia by default). If there’s no path, just remember that:
the Celestia/data folder contains *.dat files
the celestia/extras folder contains *.dsc, *.ssc and *stc files
the celestia/models folder contains *.3ds et *.cms files.
other files (pictures) belong to celestia/textures/hires folder (high resolution pictures), celestia/textures/medres folders (medium resolution pictures) and celestia/textures/lores folder (low resolution pictures and default folder for any image).
Note that some add-ons won’t run with Celestia 1.3.0.