If the skies are clear where you live tomorrow night (or tonight, depending on your time zone), don’t miss your chance to witness the last lunar eclipse until Dec. 2010.


Here in Hawaii, I’ll be heading out to the beach around 11 p.m. While I won’t be bringing my Mac with me, this event marks a great occasion to highlight a few of the astronomy programs available for OS X. These tools are excellent teaching aids and are just plain enjoyable. If you don’t have a Mac, no worries: each of these apps run on Mac, Windows, and Linux.

If you go outside to watch for the eclipse, keep an eye out for Saturn (if you have a telescope the rings will be visible) and Regulus (the 22nd brightest star in the night sky, in the Leo constellation).

Saturn and Regulus will be the brightest points in the sky nearest to the eclipsed moon. Exactly where they will appear relative to you, of course, will depend on your location and the time you go outside to have a look — but they will appear to be close to the moon.

Cloudy out? View the solar system on your Mac

1. StellariumFree. This planetarium application specializes on views of the sky from an earthly perspective. Enter your coordinates to see what's going on in your sky on a given night. This is my app of choice for casual desktop sky-gazing; it's also a great learning aid. I enjoy setting the program to fast-forward so I can watch the sky come to life in quicktime. There are many user-contributed scripts available to enhance your Stellarium experience which make an already interesting program even more engaging. This is a great program to keep on your Mac for those times when you want to quickly identify a star or constellation.
  1. Google EarthFree. It isn’t just for earth-browsing any more. Check out the ‘Sky’ view mode for a full-featured astronomy package chock full of user-contributed goodness. I’ve lost many hours engrossed in the ‘Sky’ view; this Google Earth expansion is still a pretty new feature, but it keeps getting better and better.

  2. CelestiaFree. Celestia doesn’t confine you to viewing stars from an earth-bound perspective. You are free to fly around the visible universe in dizzying three dimensions. There are many, many expansions available for Celestia that make it even more fun and valuable as a learning tool. The one thing about Celestia is that it’s not quite as easy to use as the other programs; still, it’s an amazing tool with a dedicated user base and it’s a joy to use.

  3. Starry NightExpensive. I own an old Mac OS 9 version of Starry Night Pro and I still use it on my old iBook G4 in Classic mode (note that Classic only runs on Tiger and earlier versions of Mac OS X). It’s come a long way since then and is worth checking out if you really enjoy astronomy and want a feature-rich package with many great animations and photo-realistic imagery. Even the old version of Starry Night that I own is visually very beautiful. It’s a great teaching aid to view the solar system in motion from any perspective, watch eclipses, find satellites, view the earth from distant planets, and more. If you go for the Pro package, you can hook up your Mac to your telescope to track distant objects. My only problem with Starry Night is that it seems to have gone overboard a bit with commercialization — there are now at least six SN packages to choose from, and all of them are pricey.

My favorite experience with Starry Night? Heading out in a canoe late at night with my old iBook back in my home state of Maine on Nicatous Lake (far, far away from any light pollution), turning on Starry Night’s ‘night vision mode’ and spending a few hours looking up at the sky. Note that this is only enjoyable in the summer while doused with about one gallon of bug spray to keep the mosquitos away.

More Mac astronomy links

If Mac astronomy software interests you, check out Pure Mac's comprehensive list of astronomy apps for more ideas. Hope the skies are clear wherever you may live.