This weekend I spent a lot of time playing with some astronomy software. I didn't get to see any real-life stars due to cloudy nights, but on my computer screen I saw them all, and even visited a few.

First, I played with Celestia. It's free and runs on Windows, MacOS, and Linux. The best way to think of this program is as a virtual space ship. You start out in orbit around Earth, and from there you can fly anywhere you want to. Because navigating a true 3D space is hard, there are handy short-cuts to just go and visit any object whose name you know. You can accelerate or reverse time so you can go see what a solar eclipse looks like from Sol's point of view. Several space ships and satellites are included as well, so it's fun to check up on where Cassini is right now. It's just far enough past Saturn that the planet is still large, but Titan is just a speck. And that's the main thing you learn from zooming around in space. Everything is really, really far apart. Travelling from Earth to Alpha Centauri, you see our solar system fade away almost instantly. Then nothing appears to change for a while, until suddenly you're there. There are also a ton of add-ons available for Celestia, which contain anything from better textures for Mercury to 3D models of the Enterprise. Many people have used Celestia's scripting ability to create entertaining guided tours pointing out all kinds of interesting galactic features. My only complaint really is there's no one big package available that contains a whole slew of the add-ons. Each one needs to be downloaded individually and then installed manually.

The second program I toyed with is Stellarium. Like Celestia it is free and runs on all the major operating systems. It aims to show you space the way it would look in your back yard. It immediately looks very slick, in no small part because of its use of anti-aliasing. The only configuration you really need is to select where on Earth you want your viewpoint to be. Then just accelerated time until it's night, so you can actually see some stars (or turn off the Earth's atmosphere). This program is ideal to find out what's worth looking at tonight, where a certain nebula will be, or whether Venus is up tonight or not. I then spent a bunch of time coding up a patch which greatly reduces Stellarium's framerate (and thus CPU usage) when possible. It runs quite comfortably at 2fps when nothing's going on. Some day maybe I'll try turning it into a screen saver.