Dear Roy,
What would your budget be for acquiring this setup? Judging from your earlier posts in this forum I take it that you would like to acquire as lightweight a setup as possible.
I'll answer the first query in the affirmative as I've seen great photos taken by a DSLR attached to a scope, either directly or by attaching a lens (usually a prime 24mm to 50mm) to the scope's eyepiece. However, if you wish to acquire a super-compact scope (e.g. the Nikon ED50), this would result in a very back-heavy combo that may cause undue stress to scopes of that category.
In the event that weight is a concern, the new Coolpix P300 is a great camera for digiscoping, especially if attached to Nikon scopes via a dedicated FSB-8 adapter. It is small and easily mates with the Nikon ED50 via the said adapter. In fact, its shooting rate at 7fps for JPEG is better than the 40D! See
http://www.birdforum.net/showthread.php?t=195746 for more info. personally I would say that this combo gives you the best cost and weight savings as the ED50 is Nikon's most affordable scope.
If you intend to attach your 40D directly to a scope, the Nikon ED78 (no longer in production, but available on eBay) or ED82 can give you a long 1000mm MF lens that is a tad bit slow at F13.3. My discussions with fellow member Tord on how to connect a EOS 600D DSLR to that scope can be seen on this thread
http://www.birdforum.net/showthread.php?t=200484.
In the event that you have sufficient cash, I recommend the latest scopes from Nikon (i.e. the EDG85) and Kowa that can accommodate both DSLRs or compact cameras. Both are not cheap. The EDG85 has a zoom DSLR attachment called the FSA-L2. More info here
http://www.birdforum.net/showthread.php?t=180382.
The Kowa combo has interchangeable DSLR adapters and eyepieces. It can be seen here
http://www.birdforum.net/showthread.php?t=191758.
Or you could go for a Swarovski combo instead. see
http://www.birdforum.net/showthread.php?t=77754&highlight=TLS800.
Hope this helps! :t:
Hor Kee