One of the first applications I ever saw on a (original) IBM-PC was planetarium. Additionally, in my “Navy Days” I became quite interested in astronomy, as the skies are never quite as clear as they are in the middle of the ocean!
Stellarium is a free open source and cross-platform planetarium for your computer. It shows a photo-realistic sky full of stars, constellations, planets, nebulas in realtime 3D, just like what you see with the naked eye, binoculars or a telescope. Other items like ground, landscape, atmosphere, and constellation illustrations can also be added. You can even see the Sun and Moon in their actual locations.
Notable is that you can also update the existing star charts with improved information so that even more stars can be seen in the application.
Another good competitor that you may prefer more for various reasons is Celestia, it can be found at:
Happy sky-gazing, even if it’s only virtual!