http://www.lepp.cornell.edu/~seb/celest ... ope_v1.zip
(2.5MB)

This addon works with Celestia v1.5.0pre2 and not with previous versions of Celestia. I suspect some changes will be needed for v1.5.0final.
p.s.
A Web page describing the Addon in more detail is available at
http://www.lepp.cornell.edu/~seb/celest ... scope.html
[edit]
22 Dec 2007: V2 of the Addon is now available.
http://www.lepp.cornell.edu/~seb/celest ... ope_v2.zip
(10.4MB, expands to 51MB)
[/edit]
[edit]
12Mar09: sorry, I forgot to update this. V3 became available in late December, 2008, adding control desks and more model details. It was announced in
viewtopic.php?f=6&t=13326
http://celestiamotherlode.net/creators/ ... ope_v3.zip
(19 MB expands to 88MB)
For more info, see
http://www.lepp.cornell.edu/~seb/celest ... scope.html
and
http://celestiamotherlode.net/catalog/s ... on_id=1274
[/edit]