As you've no doubt noticed, here in North America the skies are very crisp and transparent in the winter -- when the clouds have parted, of course. We also get the brightest star in the sky, Sirius, and some lovely constellations.
I've got two really well-done astronomy apps for you that have just received significant updates. One is pro-oriented, while the other is more for casual sky watchers.
First up is Sky Guide (US $1.99), an App Store Best of 2013. Sky Guide has wonderful graphics, and almost all navigation is done with gestures, leaving a very uncluttered screen. This latest version features time-lapse controls, so you can speed the sky up by 30,000 times if you want, watching planetary conjunctions and the life and death of comets. Of course, you can hold your iOS device up to the sky, and the screen will mimic your position to make identifying that star, planet or galaxy that much easier. There is also a way to have the screen match how dark your sky is -- use two fingers and swipe up and down. In very dark locations, you will see an excellent rendering of the Milky Way.
The app has plenty of built-in background articles so you can learn about the objects you're viewing, and there are some electronic soundscapes to set the mood. If you are not in the mood for music, the sounds can be turned off.
Sky Guide is beautiful, filled with worthwhile information and easy to use.
At the high end, we have SkySafari 4 from Southern Stars Software. The company has been at the forefront of excellent astronomy software for years, and the latest version of this top-of-the-line app is breathtaking in its features. The app is normally $39.99, but for the holidays, it's only $19.99 through January 20.
There is so much here, it is hard to know where to begin. The app is almost 1 GB in size, so that should give you a clue just how powerful it is. SkySafari 4 integrates with Apple Maps; choose your location and you'll see the skies on screen as they look in real life. Meteor showers are animated and look real. Time settings can take you thousands of years into the past and the future. Want to see the the skies on your birthdate, or when the Titanic sank? It just takes a few taps. The database has millions of objects, and if you have a compatible telescope, you can control it from your iPhone or iPad.
You can get photorealistic horizons for a few locations, or add your own so your backyard view looks like your actual backyard. Although things are always changing, right now SkySafari 4 is the top astronomy program of dozens of offerings by a wide margin.
If your taste and wallet aren't so ambitious, there are scaled-down, but still very powerful and less expensive versions of the app. The basic SkySafari is $0.99, and SkySafari 4 Plus is $7.99. They have smaller databases, but are very capable apps.
Sky Guide and SkySafari are designed for different levels of amateur astronomers, but both are top apps for their target markets. I heartily recommend either one for some great nights under the stars.
Sky Guide requires iOS 6.0 and is a universal app. It's an 84 MB download. SkySafari 4 requires iOS 7 and is also universal. It's a 940 MB download, so make sure you have the room to tackle this awesome app.