Celestia User's Guide
by Frank Gregorio

English MS Word document or PDF (for Celestia 1.5.1)

German MS Word document or PDF file (for Celestia 1.4.1, zipped)
 German translation by Ulrich "Adirondack" Dickmann

Romanian MS word document (for Celestia 1.3.2, zipped)
 Romanian translation by MindToAsk

French MS word document or PDF file (for Celestia 1.3.1, zipped)
 French translation of 1.3.1 guide by Jean Anglade
There's no official FAQ for Celestia yet; however, Selden Ball maintains a list of frequently asked questions here on the Celestia forum.
Celestia Wikibook
The Celestia WikiBook contains technical documentation on Celestia for users, add-on creators, and developers. Experienced Celestia users are invited contribute to the Wikibook themselves.
Additional Documentation
Please see the documentation page at The Celestia Motherlode for a comprehensive list of documentation available for Celestia. In addition to documentation for Celestia users, there are many files of interest to people who want extend Celestia by creating add-ons and scripts.

Celestia is Copyright (C) 2001-2010, Celestia Development Team