Pocket Universe: Virtual Sky Astronomy
This app is a window to the heavens -- literally.
Simply boot up it up, aim your iPad at the sky and, using its internal compass, it will tell you what constellations and stars you're looking at. You can also spin the sky to see what's beyond the horizon. Stars and planets display at the correct brightness for your location, and a simple slider lets you adjust ambient light levels to match those of your viewing location. In a city? Crank up the light, and you'll see only the brightest of stars on the screen. In a meadow in the mountains? Lower the light, and you get to see much more -- including an image of the Milky Way.
Other features include a red light mode that is easy on the eyes. A utility lets you search the app's database of all stars visible to the naked eye sorted by name, distance or magnitude. And you can browse the complete catalog of Messier and Caldwell deep sky objects (DSOs) that includes pictures of such things as bright star clusters, nebulae and galaxies far, far away.