Astronomy on the Desktop
Many people's initial exposure to science is through astronomy, and they are inspired by that first look through a telescope or their first glimpse of a Hubble image. Several software packages are available for the Linux desktop that allow users to enjoy their love of the stars. I look at several packages in this article that should be available for most distributions.
The first is Stellarium, my personal favorite for day-to-day stargazing. When you install it, you get a thorough star catalog. By default, Stellarium starts up in full-screen mode. The layout makes for a very attractive display of the sky above you, and almost all the details of the display are customizable.
Figure 1. Opening Stellarium gives you a look at the local sky.
If you hover your mouse pointer over either the bottom-left border or the lower-left-side border, one of two configuration panels appears. From here, you can set visual items, such as constellation outlines, constellation names, whether galaxies and nebulae are visible, as well as a coordinate grid. You also can set location and time values. This means you not only can see what the sky looked like in the past or what it will look like in the future, but you also can see what it looks like on the other side of the planet. Additionally, you can add even more stars to the catalog that Stellarium uses.
Figure 2. You can set the time so it's later, letting you check out what you might want to look for that evening.
Figure 3. The configuration window lets you download even more star catalogs.
To access and run scripts in Stellarium, you need to open the configuration window and click on the scripts tab. Once you've written your own scripts and want to run them, you can place them in the scripts subdirectory of the user data directory. On Linux machines, the user data directory is $HOME/.stellarium. Once you put your script files there, along with any textures they may require, they will show up within the list of scripts in the configuration window. A plugin architecture also is available, but it is much harder to use, and the API varies from version to version.
The nice thing about Stellarium is that it isn't limited to your computer. It can interact with the real world in a couple ways. The first is through telescope control. Stellarium provides two different mechanisms for controlling your telescope. The older mechanism is a client-server model. The server runs as a standalone application that connects to and controls one telescope. It then can listen to one or more clients, which can include Stellarium. Several options are available for the server portion, and they provide control for many telescopes from Meade, Celestron and others. The second mechanism is a plugin for Stellarium, which first was available in version 0.10.3. This mechanism can send only slew instructions to the telescope, which essentially are "go to" instructions.
One major warning is that Stellarium will not stop you from slewing to the sun. This could damage both eyes and equipment if you don't have proper filters on your telescope, so always be careful if you are working during the day.
The plugin can interact with pretty much any telescope that understands either the Meade LX200 interface or the Celestron NexStar interface.
The other way Stellarium can interact with the real world is as a planetarium. Stellarium can handle the calculations involved in projecting over a sphere. This way, you can make a DIY planetarium. You need a dome onto which you can project your display across the inside. You also need a video projector and a spherical security mirror. Use the spherical distortion feature in Stellarium and then project the results through the video projector and onto the mirror. Then, you can lie back under the dome and see the sky above you. The Stellarium Web site has links to groups on the Internet where you can find help and hints when building your own planetarium.
The other popular astronomy program is Celestia. Celestia is a three-dimensional simulation of the universe. Where most astronomy software shows you what the sky looks like from the surface of the Earth, Celestia can show you what the sky looks like from anywhere in the solar system.
Figure 4. When you first open Celestia, you get a satellite-eye view of the Earth.
Joey Bernard has a background in both physics and computer science. This serves him well in his day job as a computational research consultant at the University of New Brunswick. He also teaches computational physics and parallel programming.
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