TeleVue Schmidt Cassegrain 2" Everbrite Diagonal Rich Field Kit

This kit is designed to allow a premium Tele Vue 2" Everbrite diagonal attach to your SCT.

This 90° 2” mirror-type star diagonal has Everbrite dielectric mirror coatings for 99% reflectivity. In addition to higher reflectivity than a conventional aluminum or silver coated diagonal, the Everbrite coatings also provide higher contrast and resolution during critical planetary, lunar, and binary star observations. The diagonal is designed for refractors with 2” focuser drawtubes, but will also work with Schmidt-Cassegrains when using the included rear cell adapter #7785C.

The Tele Vue diagonal now comes standard with the 2" to 1.25" satin eyepiece adapter. This high hat step-down adapter allows the use of 1.25" eyepieces in 2" focuser drawtubes and 2” star diagonals. The 2" barrel of the adapter has an undercut groove that the star diagonal/focuser thumbscrew sits in when tightened down. The extra depth of this groove reduces the chance of the adapter falling out of the focuser should the thumbscrew loosen. To keep your eyepieces looking new, 1.25" eyepieces are held in the adapter by a non-marring soft brass clamp ring rather than an ordinary aluminum thumbscrew that contacts the barrel directly. The thumbscrew that tightens the clamp ring is tethered internally in the adapter so that the thumbscrew can’t be lost in the field. The body of the adapter is finished in gloss black.

The kit also comes standard with this SCT rear cell adapter.  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. 

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.

The mirror housing and its 2” focuser and eyepiece holder barrels are precision-machined from a single block of solid aluminum, rather than being simply a pair of less-rigid tubes screwed into a flimsy plastic mirror housing or sheet metal stamping, as is the case with lesser diagonals. A solid metal backplate over 4/10ths of an inch thick holds the mirror securely in place to assure permanent collimation of the diagonal’s parts. The 2” barrel that fits into the focuser or visual back is internally antireflection threaded for higher contrast. It is also threaded to accept standard 2” (48mm) filters. A groove cut into the outside of the 2” barrel acts as a safety stop to keep the diagonal from falling should the scope’s visual back or eyepiece holder thumbscrew loosen slightly from cold or use. The 2” eyepiece barrel uses a non-marring soft brass compression ring to hold eyepieces in place, rather than a thumbscrew that contacts the eyepiece barrel directly. The diagonal is finished in a non-reflective matte satin black finish.

This is an absolutely premium 2” star diagonal that will give you all the visual performance your scope is capable of delivering. It's a worthy upgrade for virtually any Schmidt-Cassegrain, Maksutov-Cassegrain, or refractor that uses a 2” star diagonal.