TeleVue Adapter to Use 2" Refractor Diagonals on Schmidt-Cassegrains

This 2.25" long by 2" diameter adapter tube allows the use of conventional 2" star diagonals (the kind that have a 2" diameter barrel that fits into a refractor's 2" focuser drawtube) on a Schmidt-Cassegrain telescope's threaded rear cell. With some smaller aperture telescopes and some 2" diagonals, the 2.25" body of this adapter may let the diagonal hit the drive base when the scope tries to swing the diagonal through the telescope forks. This can be a problem with some computerized scopes when they try to aim at the zenith while in the altazimuth mode. You will need approximately 7" of clearance between the rear cell of your Schmidt-Cassegrain and the tallest point on your telescope drive base to allow this adapter and a typical 2" diagonal (in this example a TeleVue 2") to clear the base when aimed at the zenith. If the clearance is tight, consider using the physically short TeleVue #7785SC adapter and #7782PC short front 2" diagonal to gain an extra 3/4" of clearance.

One side of the adapter is threaded to attach onto the 2" diameter rear cell threads of 8" and larger Celestron and Meade Schmidt-Cassegrains (and 7" Meade Maksutov-Cassegrains). The 2" barrel of a conventional 2" star diagonal slips into the other side of the adapter tube and is held firmly in place by a non-marring soft brass clamp ring that tightens onto the diagonal barrel without scratching. The thumbscrew that tightens the clamp ring is internally tethered in the adapter so it can't be lost in the field.