In honor of the 40th anniversary of the Apollo moon landing, astronomy apps SkyGazer and SkyVoyager are available free of charge from the App Store. Normally they're priced at $2.99 and $14.99, respectively.
SkyVoyager is a planetarium app that gives you a precise view of the sky from any position on Earth. If you have a telescope that's linked to a computer, the app can control it via Wi-Fi.
SkyVoyager features a database of 300,000 stars and 30,000 deep-sky objects. Definitely sounds like a must-have for hardcore astronomers.
If you're a beginner or hobbyist, you may want to grab SkyGazer instead. It shows you every star viewable with the naked eye and comes with hundreds of outer-space images from NASA space missions, the Hubble Telescope, and so on.
Both apps are free, but only for today (July 20). So get 'em while you can!
Thanks to reader Ricardo for the tip!