Cosmo Desktop is a beautiful Mac application that serves the latest NASA astronomy pictures http://apod.nasa.gov/ to your desktop.
You can set your Mac desktop to the beautiful Astronomy picture right to your Mac in a few clicks.
All astronomy pictures are courtesy of the NASA Astronomy Pictures of the Day under public domain, or their respective owners.
The Cosmo Desktop will always be free and ad-less. Please direct your appreciations to the APOD team by Robert Nemiroff and Jerry Bonnell http://apod.nasa.gov/apod/lib/about_apod.html.
Cosmo Desktop is also available on iOS: http://itunes.apple.com/us/app/cosmo-desktop/id553916089?ls=1&mt=12