Home planetarium project

Everyone likes to stick luminous stars on their bedroom ceiling and walls. But where to put the stars so that the view looks right?

Tips

You'll need

• a stellar catalogue of the brightest stars.
• to understand what the numbers in the catalogue mean - in particular, right ascension, declination, and magnitude
• to understand how to turn those numbers into coordinates appropriate for your bedroom. As a staging post, you could calculate the coordinates (called altitude and azimuth) that describe the height above the horizon and direction of the star; then you need to figure out where on the wall or ceiling each star should go.
• Geometry (tan, sin, cos); and by doing this problem, you'll figure out spherical geometry.
• a little computing.

My solution

I wrote a gnuplot program to go direct from the stellar catalogue to coordinates on the walls. In the program, I specify how far from my eye each of the five surfaces (four walls and one ceiling) is. Also the orientation of the room and the required time of the star snapshot. I assume the walls are all perpendicular and either horizontal or vertical.

The program creates five plots (Wall0.ps, Wall1.ps, Wall2.ps, Wall3.ps, Ceil.ps) which show where to put the stars on the five surfaces. When you've printed out the plots, you can cut them along the lines and tape them together if you want. The points (0,0) in each plot are the four points that are the closest point to your eye in each wall, and the zenith, the point in the ceiling closest to your eye.

The catalogue is contained in five files provided in this zip file [zip catalog.zip m1 m2 m3 m3.5 m4.5 ecliptic]. File m1 is all stars with magnitude brighter than 1. File m2 is all stars with magnitude brighter than 2. Etc.

David MacKay