Watch the Skies!
There was one app, though, that nearly had me writing a check to Steve Jobs for five hundred bucks.
It's a program that will show you whatever's in the sky directly behind the iPad.
So if you hold the iPad up to Scorpius, it will show the stars of Scorpius, an outline of the constellation, the other stars within the frame, and any planets that may be rambling past the scenery. You can tap on the planets and major stars and nebulae and galaxies and get a closeup view, along with a bunch of data.
It will work in the daytime. It will show you the stars on the other side of the sun or moon. It will look down through the Earth and show you the skies of another hemisphere. If you're stargazing, you'll be able to easily identify what you're looking at, or locate an object so that you can point your telescope at it. And you can dial down the intensity of the screen so it won't ruin your night vision.
But I didn't spend the five hundred bucks, so I can't tell you anymore than this.