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Celestia Users Guide
by Frank Gregorio
English MS Word document (zipped) или Read Online
Celestia Key Chart
by The Learning Technologies Project Office of NASA
English PNG Image
CEL Scripting Guide
by Don Goyette
English MS Word document or Read Online
SSC File Scripting Guide
by Ulrich "Adirondack" Dickmann and Bob Hegwood
English PDF document (zipped)
STC File Scripting Guide
by Christian Lenz
English PDF document (zipped)
Virtual Textures for Dummies Package
by Bob Hegwood
English PDF document (zipped)
There's no official FAQ for Celestia yet. However, Guckytos 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-, Celestia Development Team