There are plenty of star charts around the app store that feature augmented reality, where you tilt your iOS device toward the sky and the app reveals what planets and stars are in your field of view. Almost all are paid apps, so it's nice to see that Star Chart has gone free, although there are the inevitable in-app purchases. More about those later.
In the free version you get some very nice graphical representations of the night sky, a way to identify and learn more about what you are seeing. If you want to explore other areas of the sky without using the AR feature, just drag your finger over the screen. You can even point your screen down below the horizon and see what other parts of the world will be seeing at night.
In my tests the AR mode was accurate, so the app connection to the iPhone sensors was good and it was correctly interpreting my location, direction, and angle of the screen. The Messier Deep Sky catalog is included, so you can get some information about bright galaxies, nebula and star clusters.
The in-app purchases include meteor showers (U.S. $2.99), Extended Solar System ($2.99), Enhanced Constellations ($4.99), Extended Star Catalogs ($9.99) and Enhanced Messier Catalog ($4.99). Whew! Add in all of the in-app purchases, and you've racked up a bill of about $26.00. For that, you can get Distant Suns (Max) with similar features for $9.99.or Star Walk for $2.99. All the features don't line up across all 3 apps, but they are close enough that getting on the upgrade train for Star Chart doesn't make too much sense. Sky Safari Pro 3, which is more expensive at $39.99, has a vastly superior feature set and more data, as does Sky Safari 3 Plus ($14.99).
As an augmented reality free app, I do think Star Chart is excellent. You can pick and choose which in-app purchases, if any, make sense to you.
For a beginning amateur astronomer, the free version of Star Chart will do very nicely. I wish there was a discount for all the in-app purchases that could make upgrading a reasonable path.
Star Chart is a universal app and runs smoothly on the iPad 3 and iPhone 5 I tested it on. It requires iOS 4.3 or later, and is optimized for the iPhone 5. Our image galleries are in transition here at TUAW, so I can't post screen shots, but the app product page will show you some nice examples. The app also has a Facebook page.