Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope. It is being used in planetarium projectors. Just set your coordinates and go.
Mac OS X version of an open-source planetarium. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope.
Ok This isn't a game or mod , its more like a freeware program.
Yes, it's a program. Realistic simulations are also welcome here on ModDB/IndieDB.