Augmented reality (AR) apps have really taken off in the last two years. Hidden Sky is an augmented reality application for the iPhone 3GS and iPhone 4 that allows you to explore the many satellites that orbit the Earth, the planets, and other objects in the sky. While it isn't free and will cost you $4.99, for those of you keen on Astronomy, you can observe orbits, animate across the sky, learn about them, and much more. It looks to be a comprehensive app that should be well worth your money.

[via iTunes]