April is Global Astronomy Month. The following apps offer fun and educational ways to learn more about the stars.Apple appsStar Walk -- 5 Stars Astronomy Guide ($2.99) Point the Star Walk app toward the sky, and it will identify the stars, planets and constellations in your line of sight. (Mobilewalla Score: 97/100)Redshift -- Astronomy ($11.99) An extraordinary 3-D encyclopedia of the vast majority of explored space objects, including 500 galaxies. (Score: 88/100)Solar Telescope HD ($1.99) Provides a safe means to observe the sun's changes in real time. (Score: 77/100)Astronomy 101 By WAGmob ($1.99)* A learning tool designed to help students of astronomy learn the basics and test their knowledge. (Score: 69/100)Astronomy Challenge (Free) Test your knowledge of astronomy with this fun quiz. (Score: 66/100)Android appsSky Map (Free) Identify objects in the sky instantly with Sky Map. Simply point your device at the sky, and it will give information about what's above you. (Mobilewalla Score: 98/100)NASA App (Free)* Follow the amazing discoveries and view the most recent images collected by the NASA team. (Score: 95/100)Mobile Observatory -- Astronomy ($4.49) A sophisticated tool for astronomy fans featuring a live sky map and alerts for special events that are worth viewing. (Score: 90/100)Space Images (Free)* View stunning photographs of the universe's wonders, brought to you by the Jet Propulsion Laboratory. (Score 88/100)Sun Surveyor ($6.49)* Real-time and predicted explanations of the position, light intensity and angles of the sun; this app is a great help to photographers. (Score: 81/100)An asterisk* denotes availability on Apple and Android.Mobilewalla is a search-and-discovery engine using breakthrough technology to score every app to help consumers navigate the mobile application marketplace. Apps are scored using an algorithm that weighs several characteristics, including user ratings, position within category and staff recommendations. For more app intel, go to www.mobilewalla.com. Anindya Datta is a technologist and founder of Mobilewalla.