Google Sky Map [Free] is an app made to complement Google Earth. Essentially it is the same thing, but with stars, constellations, and planets.
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Pro Clearly lists what is being viewed
When the phone is aimed at a certain star, the name of the star (or stars) will come up on the screen. This app lists names of stars, constellations, and planets.
Pro Layers can be chosen
For users who are looking for a particular planet, star, or constellation, all other listings in the app can be disabled except for the target.
Pro Search function for finding specific objects
As long as the name of the star or planet is known, it can be found using this app. It is much easier to find an object using the in-app search function than trying to locate it based on other stars or planets. Once the object is searched, an arrow will be displayed that directs the user to the right location in the sky.
Con Requires GPS to be activated
Sky Map won't work without GPS.
Con Hard to navigate
Depending on the environment, Sky Map can be hard to use because of the app's controls and the current visibility.