> ...quality of the glass in a scope, even a high end swarvoski AT80HD
> or Leica Trinivid 77 does not compare to what you would find in a
> high quality Canon or Nikon SLR lens (and i'm not talking about
> some massive zoom lens here, but rather something along the lines
> of a Canon 500mm f/4L IS USM or Nikon 500mm f/4 AFS ED-IF or
> some such similar lenses...300mm f/2.8, 600mm f/4, 400mm f/2.8
> etc).

This surprised me. I realize there are many differences in spotting scopes
and telephoto lenses, but I didn't realize that the quality of the glass was
one of them (given that both are top of the line). Quantity is a different
story <G>. Chris, do you have any references or head to head comparisons
you can point me to? I would be very interested in researching objective
evidence on this.

> I'm not at all sure why you'd want to do this.

The two primary reasons I can think of for attaching a DSLR to a spotting
scope are cost and portability.

Given equal equivalent focal lengths, a spotting scope is less expensive
than a telephoto lens. The spotting scope is nice if you are both bird
watching and photographing, and many birders have a spotting scope already.
In addition, again with equivalent focal lengths, the spotting scope is much
lighter and more portable.

With that said, I have heard from others that taking photos with a DSLR
attached to a spotting scope is not easy. Echoing what Chris said, spotting
scopes let in much less light. This can make it hard to see the bird via
the camera, hard for the camera to autofocus, and to get a good shutter
speed requires high ISO settings that introduce more noise in the
photograph. Given the option, I personally would put the adapter dollars
into a good telephoto lens. This is especially true for an active, moving
bird (very hard to photograph by digiscoping).

Given an equivalent lens, you will always get a better photo with a DSLR
using a telephoto than by digiscoping. However, <grin> I would also
purchase a digicam and digiscope as well. Using a digicam with a spotting
scope has the above advantages, reduced cost and portability. If you are
out birding with your scope, it's easy to toss a digicam into your bag too.
In addition, digicams use a small CCD (where the image is recorded) and
therefore concentrate the light from the digiscope. This gets around the
big problem of digiscoping with a DSLR noted above. The small CCD with a
spotting scope produces the effect of a very fast lens with a field of view
equal to a very long telephoto lens, so you don't have to be as close to the
bird. You can easily see what you are photographing, and autofocus
typically works well. Also, the mirror slap of a DSLR causes significant
vibration, where the leaf shutter of a digicam is much "softer". (Some
photographers complain about how birds react to the mirror slap too.)
Digicams photos are lower in quality. They have more noise, and the complex
optical path theoretically can have an effect (I suspect that high-quality
glass spotting scopes provide an image that is at or near the resolving
power of a digicam's CCD). However, with a bit of digital developing
knowledge, a 5 MP digicam photograph can easily be printed at very good
quality to 11x14. I routinely print photos from my 3 MP digicam at 11x14,
and photographers I have shown them to assume they are 35mm enlargements. A
typical photographer, I'm always eager to share my photos as an example
<smile>:

http://www.featherphotography.com/gallery/

(Be aware though, it is difficult to compare photographs at resolutions used
on the web.)

Caren, a great place to research digiscoping, including adapters for DSLRs,
is the Yahoo Group Digiscoping Birds located at:

http://groups.yahoo.com/group/digiscopingbirds/

As always, YMMV,

John
www.featherphotography.com