Celestia is a dreamer's software, but in the same time is one heck of a challenge. Amazingly there's a ton of astronomy software out there, most of them working on every major platform, but feature wise, Celestia has to be one of the most complex and fun to use in this really narrow niche.
Celestia was originally built by Chris Laurel, but lots of other developers have join the team over the years. Known under the name of Celestia Development Team, these people have managed to construct a software that is actually used by NASA (National Aeronautics and Space Administration) and ESA (European Space Agency) in a teaching capacity.
Installation
The developers provide a source package for version 1.6.1, which is also the latest one, but good luck on trying to compile and install. It has a ton of dependencies and it will take some time just to get ./configure to run (it also needs a second parameter, like KDE and GNOME, to specify which desktop environment you are using, but it's all detailed in the readme file).
After I got ./configure to run successfully, the make command churned out several errors. I had no time to figure out what needed to be fixed, but maybe some of the users will take the time to get it to work. So, instead of reviewing 1.6.1, I had to review 1.6.0 which can be found in the Ubuntu software repositories.
The latest version comes with a few improvements, and the most interesting are the new extrasolar planets and the updated Galileo add-on. There are also lots of fixes, but there shouldn't be major differences.
Usage
Celestia can be a little intimidating at first, especially because it seems to appeal to a more scientifically inclined fan base or to people that actually know what they are doing. Users have to remember that besides the complexity of the software, Celestia is designed primarily to be a teaching instrument.
The program first opens with our Sun in view and then it switches to Earth. After that, regular users will spend tens of minutes jut clicking around in the sky, randomly, wondering what is the name of that shiny dot and how far is it. Eventually they discover the zoom function and realize they can actually go outside of the Milky Way (the software also includes other galaxies from the local cluster).
In its basic form, Celestia encompasses more than 120.000 stars and uses the Hipparcos Catalogue as a database. Hipparcos was a scientific experiment that gathered precision astronomic readings about stars, like distance, trajectory and speed.
In Celestia, users can travel to any of these stars (extrasolar planets, and a few new stars were also added) just by clicking, at any speed and more importantly, at any given time (past or future). It also has tons ot other features like a comprehensive star catalog, a solar system browser, a simple search that can be used without much astronomical knowledge and even time speed.
Even with so many interesting features, Celestia would just be a simple program, but it turns out the strength of this software doesn't consists in what it initially provides, but in its add-ons. There are almost 20 GB worth of add-on available, ranging from high-resolution textures for Earth and all the planets in our solar system, to recreations of famous TV shows like Babylon 5 and Star Trek, and even the universes from some video games.
All these goodies can be found on an associated website (www.celestiamotherlode.net). Users will loose hours on this website just to check out how did the original Appollo mission looked like, what are the most dangerous comets and asteroids that roam in our neighborhood and what was the home planet of Jabba the Hut.