As an optional part of the T-2 Astro Modular system, you can use the Alpine Astronomical Baader 3.3" SCT Visual Back Nut to mount their 2" eyepiece holder, or other compatible gear, onto larger Schmidt-Cassegrain telescope (SCT) visual back threads such as the Celestron C11 or C14, without vignetting. The nut has a circular dovetail V-mount with a series of set screws to hold the holder securely in place without rotating or tilting.