Referring to David Burren's reply on this topic, where he mentions using
T-mounts. This adapts an SLR to the spotting scope directly, with no
lens on the camera or eyepiece on the scope, which is optically quite
different to digiscoping as I understand it, which involves pointing the
camera into the scope eyepiece, normally using a bracket to couple the
two. I think one of the most important things is that the eyepiece has
long eye relief as the front element of the lens needs to be inside the
eye relief distance of the eyepiece. If this is not met, you get
vingetting and is a mechanical issue quite independent of optical
quality. see: http://www.digibird.com/whatisdir/whatis.htm
When using the T mount you are using a Prime focus setup and the focal
length may be about 800 mm. Pointing the lens into the eyepiece is
called afocal projection and allows much higher magnification, and
apparently much sharper images, it also appears to allow you to do this
without a huge penalty in speed of the system.
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