Astronomy Software
Michael Poxon

Alien Skies

Alien Skies is a Windows "Planetarium" program with a difference. It shows not the sky of Earth, but that of other stars! As long as you know the position of the star whose sky you want to draw, you can pick any star you like - you can even invent one! You can choose to plot as few or as many stars as you like in your alien sky, and set the threshold above which stars appear coloured as well as the distance units you want to enter (choose between light-years or parallax (seconds or milliarcseconds)).
Alien Skies 1.0 (the current version) comes with a default database of over 1000 stars (which you can add to) in the sky of Castor, one of the twins of Gemini. You might be interested to know that from Castor, both Capella and Pollux appear as bright as Sirius does to us, while the Sun is barely visible with the naked eye.
The database contains all those stars above magnitude 5 as seen from the Earth, plus several more (to us) faint stars which do, however, appear bright as seen from Castor. Since the application is database-driven, as soon as you enter a complete set of data for each star, it is saved automatically. There is no "Save" item on the menu!
Once you have a sky view you want, you can save it as a bitmap. The sky view is customisable for such features as sky background colour, star-label colour and font, gridline format, magnitude limit, etc. Clicking on the sky view will display the accurate position under the mouse.
Alien Skies comes with extensive help files, including an astronomical glossary for those unsure of some of the terms used, and a little animation showing the theory behind the program.
Version 2 will simply allow you to choose from a list of some notable stars and draw their sky automatically.

Precession Calculator

With the passage of the years, the Earth's axis traces out a circular path due to the gravitational influences of the Moon and Sun, taking over 20,000 years to make one revolution. This means that the accurate positions of sky objects also change, since the co-ordinate grid we use to define them is based on the Earth's axis! This change in position is called precession, and with the Precession Calculator you can obtain accurate positions for either the past or future, from original positions given for the "Standard Epochs" of 1900, 1950 and 2000.

Download Alien Skies (c. 25MB zipped file, contains all support files)
Download Precession Calculator (c. 3MB, contains all support files)