Today's smart phones provide users with the equivalent of a pocket computer, making tasks easier and reference sources immediately available. Amateur astronomers can take advantage of this by using available apps to more easily explore the sky and target what they are looking for. Both the Android and iPhone platforms have a large selection of available astronomy applications, here is a list of good apps to try out:
Star Chart (free) - Accurately depicts over 120,000 stars, displays 88 constellations, and includes the entire Messier catalogue of deep space objects. Supports dynamic device orientation viewing which allows the user to view the night sky regardless of the angle of the Android device. Star Chart is fully configurable, which allows you to display only the objects that you are interested in viewing.
SkySafari ($2.99) - Accurately shows you the sky from any place on Earth, at any time up to one hundred years in the past or future. It includes encyclopedic descriptions of the constellations, stars, and planets written by professional astronomers. And it contains hundreds of images from NASA space missions, the Hubble Space Telescope, and the world's foremost astro-photographers.
Distant Suns ($4.99)- A point and locate app with information on over 300,000 stars. It uses images from the Hubble Space Telescope and includes data and information on everything you observe. It also provides you with weather updates so you know when your view might be blocked by cloudsand push notifications so you don't miss important space events.
Mobile Astronomy ($4.99) - Mobile Observatory is one of the most complete astronomy apps on the Android market and the perfect tool for anybody interested in the sky's wonders, from the occasional sky gazer to the passionate amateur astronomer. Think of this as a complete Astronomy 101 resource at your fingertips.
SkEye (free) - SkEye is an advanced Planetarium that can also be used as a PUSHTO guide for telescopes. Ever wondered what objects are up in the sky? Now you can get familiar with Astronomy by identifying stars, planets, and constellations. Also look up deep sky objects from the Messier and NGC catalogs. If you have a telescope, just strap the phone onto the OTA and you get a PUSHTO guide!
Moon Atlas ($5.99) - Moon Atlas is an astronomy application that lets you use pinch and finger gestures to manipulate a 3D globe of the Moon. This is a rendered sphere and not a static map image. As you zoom in more labels appear as finer detail comes into view. You can double tap on the labels to get more information on over 1800 named features.