The Astro-Tech Variable Camera Adapter consists of three parts for both prime focus and eyepiece projection imaging with 1.25" focuser refractors and reflectors. It is generally not used with Schmidt-Cassegrain or Maksutov-Cassegrain telescopes, as these telescopes have their own thread-on adapters.
The 1.25" barrel prime focus section of the Astro-Tech adapter is used by itself (or with an optional T-ring) for prime focus lunar, and terrestrial photography. The one-piece prime focus section is made of CNC-machined aluminum, anodized matte black, with matte black internal anti-reflection threads. Its one-piece construction assures that the 1.25" barrel cannot become unscrewed from the T-thread portion, as can happen with two-part chrome barrel adapters. The prime focus section weighs eight-tenths of an ounce.
The prime focus section and two-part eyepiece projection section of the Astro-Tech adapter are screwed together for high magnification eyepiece projection photography (using the same optional T-ring).
The eyepiece projection section consists of two nested tubes, weighing a total of 6.4 ounces. Each section is made of CNC-machined aluminum, anodized matte black, with matte black internal anti-reflection threads. The outer tube (with male T-threads on one end, to which the CCD camera or optional T-ring attaches) can be shortened or lengthened to change the projection distance from 90mm to 125mm. The telescoping outer tube is held firmly at the desired projection distance by two thumbscrews.
A separate thumbscrew holds an eyepiece firmly within the inner tube to project the image from the telescope back to the camera focal plane. The variable projection distance design allows you to change the magnification to vary the size of the image by 44% without the need to change to a different focal length eyepiece.
Eyepieces with rubber eyecups may not fit into the camera adapter without temporarily removing the eyecup. The maximum eyepiece o.d. that will fit into the adapter is 36mm (1 and 3/8"). The Astro-Tech Variable Camera Adapter needs an optional T-ring for use with 35mm and DSLR cameras. The 1.25" prime focus section is threaded for 1.25" filters. The calculator below is set for a 90mm projection distance.
