Stellar software Stellarium

For those who are interested in sky observing, Stellarium is software worth having a look. Released under GPL and available for many platforms, it gives nice views of the sky (including star positions, planets, moon etc) as it will be when viewed from anywhere in the world. You can select the location by specifying latitude and longitude, or select a city from its built-in database.

This is not your average shareware software. This is completely free for personal, commercial and any other way you want to use it. It has no trial periods or limited functionality. No registration required. Just download/install/use. You can copy to as many machines as you want unlike most copyrighted software. Even the source code is available for free, hence its called Open Source Software.

For comparison of whats simulated and whats actual, the following picture shows how Stellarium shows the moon smiling on us on 1st Dec 2008 at 1900hrs when viewed from Male'.

Compare that to an actual photograph taken the same night about the same time. The exposure of the moon and planets are different because Stellarium cannot simulate the atmospheric light scattering (and the photographer's shaky hands!).

You can view other astronomical events of the past and the future. Just for the record, 20 Dec 2009 is the start of the Mars' retrograde motion (meaning Mars appear to reverse its direction of motion, until 10 March 2010), which you can view exactly how it is going to look from Earth as shown below. Good explanations available for anyone who care to read. No fear mongering please this time.

The planet Mars is centered on the screen. You can see the planet moving left relative to the stars (it is actually moving eastwards relative to the stars). The date is shown on the lower right of the video. Starting on 1st Nov 2009, the video shows Mars slowing down around 10 Dec 2009, and reversing the motion on 20 Dec 2009. Though the video shows until end of January 2010, this retrograde motion continues until 10 March 2010. You can also see the wobbly motion of the moon as well.