Great program! Just noticed that nineplanets.org and celestia disagree on a suitable URL for information on pluto's moon, Charon
http://www.nineplanets.org/pluto.html#charon
- actually exists, and describes the planet
http://www.nineplanets.org/charon.html
- celestia tries to load this page, with 404 response
(other planets are correctly listed on their own page)