This program is an observing aid, but it could also be useful to teach geometry, orbital mechanics and even special relativity. (I admit that these topics may be a little deep even for high school students!)
 Priorities for next release
I'd like to animate the display, perhaps at a rate of one hour every five seconds.
The program also needs localization. I'm supplying EN (because that's what it was developed in). Other languages would be nice.