On the night of Dec. 20-21, a total lunar eclipse will dress the moon in holiday red for more than three hours. For 72 minutes of that eclipse, the Earth’s shadow will hide the moon in complete darkness.

This unusual celestial event is visible for hundreds of millions of viewers across North America. The last year North America saw a total lunar eclipse on the winter solstice was 1638. The next is 2094 — making this event a once-in-a-lifetime opportunity.

To ensure people can track this eclipse, Southern Stars is releasing the latest version of its SkySafari LiteT iPhone app for free through Dec. 22. SkySafari Lite is an app that correctly predicts and displays this eclipse. It features research-grade accuracy, the largest celestial database of any mobile planetarium app, and descriptive content written by experts. To download SkySafari Lite now, go to http://itunes.apple.com/us/app/skysafari-lite/id321419308?mt=8. More info, including video and a link to the app, can be found at http://www.southernstars.com/eclipse/index.html .

Southern Stars is also announcing a update to the “pro” version of SkySafari. This free version 2.1 update brings support for SkyWire, a new iPhone accessory for telescope control from an iPhone, iPad, or iPod touch. SkyWire plugs directly into an iOS device dock connector, and provides a link to a telescope’s serial interface. For more info on SkyWire, go to http://www.southernstars.com/products/skywire/index.html .