Celestron - Radial Guider

Specifically for use in prime focus, deep-sky imaging or astrophotography with
Schmidt-Cassegrain telescopes, the Radial Guider is compact and sleek in design. This accessory
makes it possible to simultaneously photograph and guide through the optical tube assembly of
your telescope. The Radial Guider also eliminates the problem of differential flexure, because
you’re both guiding and photographing through the telescope. 
The Radial Guider is
compatible with Celestron’s C5, C8, C9¼, C11 and C14 telescopes and comes with a unique prism
angle adjustment screw. It must be used with a guiding eyepiece, camera T-Ring and drive
corrector (dual axis preferred). Primarily for use with catadioptric telescopes, but also works
on refractor telescopes having adequate back focus. 
This guider is a tremendous
improvement over conventional off-axis guiders. Not only is the angle of the prism tunable, but
it also maintains a fixed rigid camera orientation while still offering users the freedom to move
the guiding eyepiece radially about 135°.