What are some alternatives?
When comparing Celestia and Solar System Scope, you can also consider the following products
Space Engine - Space Engine is a realistic virtual Universe you can explore on your computer.
Stellarium - Stellarium is a free open source planetarium for your computer.
KStars - KStars is a Desktop Planetarium for KDE.
Gaia Sky - 3D visualization software for ESA's (European Space Agency) Gaia mission to chart about 1...
Sky Map - Sky Map (formerly the Google Sky Map) turns your Android-powered mobile phone into a window on the...
Universe Sandbox - Universe Sandbox ² is a physics-based space simulator.