No stars? No problem

This month's unseasonably cool and overcast weather has put a damper on all kinds of outdoor activities, including skygazing.

What you may not know, particularly if you're new to the hobby, is that there are a number of free software packages that let you explore the heavens from the comfort of your desk. It's the next best thing to being in your backyard with a telescope. We'll take a quick look at three of the most popular options, each of which is available for both Windows and Mac.

Google Sky

Google Sky is not a separate software package, but is rather a mode available in the free Google Earth software package (which is something you should install on your computer in any case).

To access Google Sky, launch Google Earth and look for a button with an icon of a ringed planet on it. If you select that button, you'll see four options: Earth, Sky, Moon, and Mars. I could write multiple columns just about these four modes of Google Earth―and I encourage you to play with each of them―but let's focus on Sky for the moment.

Much as Google Earth presents you with a 3D map of the entire planet, Google Sky presents you with a 3D map of the sky, viewed as though it were projected onto the interior of a sphere.

The interface is simple and straightforward, allowing you to key in the names of objects you'd like to see, e.g. Mars or the Andromeda Galaxy. Google Sky will pan and zoom to the object, just as it would if you'd punched "West Chester, PA" into Google Earth.

Google has supplemented the star chart with thousands of high-quality astronomy photos―try that Andromeda Galaxy example―but it's more of an educational tool than a skygazing aid. There's no simulated horizon, and there's no way for Google Sky to tell you what you should expect to see from your own backyard. For that, you can use...

Stellarium

Stellarium is designed with the skygazer in mind. In order to show you what's in your night sky right now, Stellarium provides you with the ability to specify your location on Earth. You can do this by selecting a town from a very long list of places around the world―Pottstown, Norristown, and Lansdale are all in there―or, if that's not precise enough for you, you can enter your exact location via latitude and longitude.

Stellarium then presents you with an interactive simulation of the sky as seen from the location you've specified at the time you've entered (the default, as you might expect, is the current time and date, but you can enter any date you like to see the sky as it appeared at that time). Click on individual stars or planets to view additional information on them.

There are configurable options for virtually anything you'd like to look at while you're outside. You can even take your own photos of your backyard observing area and create a landscape image file so that Stellarium's display accurately depicts the locations of your house, trees, and other objects that might obscure some portions of the sky.

Stellarium is arguably the most useful piece of software available for the backyard astronomer. If you own a portable computer, consider loading it up and taking it outside with you for your observing sessions.  There's even a "night mode" that changes all the whites and blues into shades of red so that you don't wreck your dark-adjusted eyes by taking them off a dim sky object to check your bright laptop screen!

Celestia

This is perhaps the most powerful and most sophisticated of the free sky simulators. To call it a sky simulator does it a disservice, really, because Celestia (see the accompanying Youtube video) actually simulates the known universe in 3D.

When you launch Celestia, you'll be presented with a 3D image of the Earth. In the background, among the many thousands of stars represented, you'll see the familiar outlines of our Earth-based constellations.

To get an idea of what Celestia can do, pick one of the thousands of stars you'll see in the background. In the upper left, you'll see the star's official designation, it's distance from your current position in space, and some other information.

Now hit "G" for "Go."

Zoom! Watch the familiar constellations get distorted beyond recognition as you careen across space at impossible speeds towards a close-up rendezvous with the star you selected.

Now hit the asterisk (*) key to look directly behind you. Can you pick out our Sun? Unless you went to a pretty nearby star, probably not.  It's back there, though, just another anonymous medium-sized G-class star among billions.

Don't worry about getting lost in deep space, though. Hit "H" (for "Home") to select our Sun, and hit "G" again to come back to the good old Solar System.

Kill a rainy afternoon by flying around each of our neighboring planets, all faithfully reproduced for your touring pleasure―or get a sobering idea of exactly how mind-boggling large the universe is by soaring out of the Milky Way and paying simulated visits to galaxies millions of light years away.

In the sky now

They peaked on Thursday night, April 21, but the meteors of the annual Lyrid meteor shower will continue into Monday.  If you spend 15-20 minutes outside looking at the northeast sky, you should be able to catch two or three decent shooting stars.