Joshua Bury has Observer Pro Astronomy Planner (iTunes Link) for the iPhone and iPod Touch in the iTunes App Store for FREE (regularly $9.99) for a limited time.

Observer Pro is a groundbreaking app for advanced astronomy planning. No more guessing when that galaxy emerges from behind that pesky tree. No more estimating how many hours you’ll be able to image an object. Observer Pro gives every astronomer the info they need right at their fingertips!

Note: the current version of Observer Pro is not compatible with iOS 8. The developer is working on a fix.