Astronomy on the Desktop

Celestia has a powerful scripting engine that allows you to produce tours of the universe. When you install Celestia, you get a script called demo.cel that gives you an idea of its capabilities. The add-on section of the Celestia Web site includes a full repository of available scripts.

Because so much work has been done to make it as scientifically accurate as possible, it also is being used in educational environments. Currently, 12 journeys are available that provide information for students and the general public on the wonders of the universe. As opposed to scripts, journeys give you more control over your speed and pace, allowing you to take more time at the areas that are of most interest to you.

When you install Celestia, you get the core part of the program and a few extra add-ons. Currently, more than 500 add-ons are available, and if you install them all, you will need more than 18GB of drive space. The main repository you should check out first is located at http://www.celestiamotherlode.net.

If you want to travel to another planet in the solar system, you can click on Navigation→Go to Object. Here you can enter the name of the object and how far away you want to be. Then, click on Go To, and you'll be taken there directly. Once you're there, you can rotate your camera view with the arrow keys. In this way, you can go to Mars and turn around and see what the sky looks like from there.

Figure 5. When you want to go to an object, you can set what object you want go to and how far away you are.

Figure 6. You can zoom in to see the Great Red Spot on Jupiter.

Figure 7. You can look out and see the night sky on Mars.

If you want to move around the orbit of the body you're currently at, you can use the Shift and arrow keys to slide around and see the whole surface. What you see when you are in orbit around another planet is a texture mapped onto the body.

Celestia's core installation includes a minimal set of textures that strive to be as accurate as possible. You can change the textures being used by including add-ons from the repository. Some of these include textures that allow you to see what the Earth may have looked like during the last Ice Age or even four billion years ago.

In 2007, Vincent Giangiulio created an add-on called Lua Edu Tools. This add-on provides all kinds of extra functionality to Celestia. A toolkit is displayed on the right side of the screen that provides sliders for controlling many of Celestia's parameters. It also provides a "cockpit" overlay, making it feel even more like you're flying through space. The default texture is the space shuttle, but you can use other ones too. Celestia also lets you use a joystick to control movement, so you can immerse yourself completely into your dream of flying through space.

You can share your experiences with others by saving still images or movies. If you click on File→Capture Image, Celestia lets you save a PNG or JPEG image file. Clicking on File→Capture Movie lets you save a movie of your travels. You can set the aspect ratio, the frame rate and the video quality. Once you click Save, Celestia will be ready to start recording. When you are ready, click the F11 key to start recording. When you're done, you can stop recording by clicking F12.

This article is only an introduction to what you can do. Hopefully, it inspires you to go explore the universe on your desktop. From there, bundle up and go spend the night out under the skies. You won't regret it.