Sky Safari is an excellent resource for both the beginner and veteran stargazer – SkySafari Review

First and foremost, this app is very user friendly, even for an extreme neophyte. This is an amazing app that shows your location under the celestial sphere and allows you to zoom in on any object of interest, from constellation to deep sky object, at will. You are also able to see objects of interest below the horizon in anticipation of later viewing. This app keeps track of the sky 24/7 at your location, even during the day, reminding you that the stars are still there even when the Sun is shining. This helps the beginner learn the celestial seasons with the reassurance that in six months this same invisible daytime sky will become the nighttime sky yet again. This app will send you notifications of selected sightings of predicted events such as ISS (Zarya) crossings.
Review by ecliptomaniac on SkySafari.