Star Walk [iTunes link] has been updated and improved with new features that let you leave the earth and look back at our home planet in beautifully rendered views.

Star Walk uses GPS to get your location, and shows you the current sky above your head. Since we last looked at Star Walk the app has added augmented reality, so as you orient your phone to the sky (iPhone 3GS only) you see star maps that show just where you are pointing. You can zoom into any object and get a closeup view of the surface details of planets, or even close-ups of deep sky objects like star clusters, nebulae, and galaxies. You can click on a button and get more info on the object, and if that isn't enough you can connect to Wikipedia for even more.

Star Walk is one of the great demos of Apple technology. Standing out on any clear night, exploring the skies, and easily finding out what you are looking at is a real treat.

I think the earth view is nifty, but frankly, it probably isn't a feature you will use a lot. On the other hand the augmented reality features, the detailed star maps, and close-up images of objects in our solar system are very compelling features.

I still don't like that the app switches to Safari for the Wikipedia info. It would be nice to see the browser built in, but that's a small price to pay for the rest of the deep information provided.

Star Walk works on any iPhone or iPod touch with version 3.0 or later software. The augmented reality feature, as I said, only works on the iPhone 3GS.

At US$4.99 there is a lot to like in this program. Even better, we have ten free licenses to give away to our readers. Here are the rules:

• Open to legal US residents of the 50 United States and the District of Columbia who are 18 and older.
• To enter leave a comment on this post.
• The comment must be left before Monday October 5 at 11:59PM Eastern Daylight Time.
• You may enter only once.
• 10 winners will be selected in a random drawing.
• Prize: One copy Star Walk (Value: US$4.99)

Click Here for complete Official Rules.

Hare are some more screen shots of Star Walk to whet your appetite:

In this International Year of Astronomy we're seeing a small explosion of astronomy apps updated both for the Mac and the iPhone.

One of my favorites, Distant Suns [App Store] has updated the build that runs on the 3GS iPhone to include some augmented reality features. This means that if you point the phone up to the sky, the program figures out the direction you are pointing and your elevation and slews to the proper view of the star map, giving you a view that should match what you are seeing in the sky.

This greatly enhances the usefulness of this program, especially for novices who want to get outside under the summer stars and quickly figure out 'what's up?'.

This new version is only for 3GS iPhones, and an update with some additional features for all the earlier models is on the way. Of course older phones won't have the compass feature. Other changes include some UI tweaks, and setting the sound effects default to 'off.'

Pocket Universe [App Store], which I reviewed last month, has a similar feature and also works very well. Pocket Universe sells for US$2.99 and Distant Suns is $5.99. Check reader reactions to both and go into details on the features to decide which one is right for you.

Distant Suns has a long pedigree in the star mapping world. It first ran on the Commodore Amiga in 1987, then was ported to the PC, the Mac, and now your favorite cell phone.

When you look up at the moon this summer to celebrate the Apollo 11 landing 40 years ago, be sure to investigate the thousands of other points of light with a software app that will literally point you in the right direction.

Note: Distant Suns runs on the iPod touch as well, but the software will not have the augmentation/orientation feature because the magnetometer isn't present in the iPod touch hardware.

I've always loved astronomy. There is something about the tremendous size and scope of our observable universe that is inspiring and humbling at the same time. It's why I get excited about the variety of astronomy programs for the iPhone.

The latest is called Pocket Universe [App Store link]. For the $2.99US price, your iPhone or iPod touch gets a star atlas of 10,000 objects, a guide to moon phases, a list of what's up on any particular night including meteor showers and any visible planets, as well as live links to astronomy news.

The app also includes an accurate rendering of the positions of the 4 easily visible moons of Jupiter, but your best bet in seeing a planet this time of year is Saturn which is high in the southeast.

As we move toward summer, more and more people will be heading outdoors. That makes it it is a great time to learn the constellations and be able to understand what you are looking at, as opposed to just wondering what that bright thing is.

A nice feature of the app is auto tilt, so when you are pointing the right direction, you can tilt the phone up to get a view higher in the sky and the star map will follow your tilt. If, as rumored, the iPhone adds some kind of direction finding compass, apps like this can be even more helpful as you turn and tilt, as the map should track your movements exactly.

Pocket Universe has a very clever locate feature, where you can select an object, and there are on-screen directions to take you to the object by superimposing arrows on the screen. This feature didn't always work perfectly. I asked the program to find Saturn. It told me to follow the arrows, but no arrows appeared. It seemed to work fine on other objects I was looking for, and Saturn was properly placed on the sky map.

How does this object compare to some of the competition? Quite well. It's reasonably priced, and with the live links it has some features the others don't have. I also recommend Distant Suns, Starmap, and Star Walk as worthy alternatives.

Here are some screen shots: