GSO 8" f/8 Ritchey-Chretien Astrograph Telescope - Steel OTA (White) #RC-8-W

1. Overview Widely used in professional telescopes around the world, the Ritchey-Chretien (RC) design offers many advantages for serious astronomical imagers. RC scopes use primary and secondary mirrors ground to precise hyperbolic figures, which means they suffer little of the ...1.

Overview Widely used in professional telescopes around the world, the Ritchey-Chretien (RC) design offers many advantages for serious astronomical imagers. RC scopes use primary and secondary mirrors ground to precise hyperbolic figures, which means they suffer little of the aberration and coma that plague Newtonian telescopes. They have flat fields that provide pinpoint star images right to the edge of the field of view.

They do not require a corrector lens, so they have no chromatic aberration like refractors or Schmidt-Cassegrain telescopes. And they have open optical tubes, which can make it easier to come to thermal equilibrium with their surroundings. The difficulty of figuring the optics of an RC meant that these telescopes have, in the past, been prohibitively expensive for amateur astronomers.

But modern materials, design, and manufacturing techniques have enabled the production of high-quality RC scopes that are remarkably affordable. The RC Ritchey-Chretien assemblies produced by Guan Sheng Optical (GSO) offer superb value to intermediate and advanced astronomical imagers who are looking for a longer focal length scope to use with cropped sensor and full-frame DSLR cameras, as well as nearly all dedicated astronomy cameras, including video cameras for electronically-assisted astronomy (EAA). These scopes come with precisely figured optics, baffled tubes for superior image contrast, and rugged and precise dual-speed focusers to securely hold your camera and accessories.

(NOTE: This telescope is equipped to accept 1.25” and 2” eyepieces for visual use, and it does produce acceptable visual images. However, it is primarily intended for imaging applications. Observers looking for a compact and longer focal-length OTA for visual observing should consider a Schmidt-Cassegrain or Newtonian telescope.) 2.

Full Optical and Mechanical Testing and Quality Control - An Agena Exclusive! GSO telescopes are available from several suppliers, but Agena does much more than simply move the telescope boxes from GSO to you. Every GSO telescope is inspected to ensure good cosmetics, collimation, smooth focuser operation, and to make sure all parts are included by the manufacturer. This is a qualitative method to evaluate primary mirror smoothness and figure.

Note that these tests are qualitative and no detailed test reports are included. 3. Optics and Tube This RC OTA comes with 200mm (7.9”) mirror with a 1600mm focal length, giving it a relatively fast focal ratio of f/8 in a compact steel tube that’s only 18” long.

The precisely figured hyperbolic primary mirror is made from quartz for enhanced thermal stability. Quartz is superior in thermal characteristics to BK7 glass or soda lime float glass - the glasses used in consumer products like cookware - that's used in many reflectors in this price range. The mirror is coated with enhanced aluminum to a nominal reflectivity of 95% and coated with a protective layer of SiO2 (quartz) for durability.

The primary mirror is mounted in a fixed cell that’s heavily baffled to prevent stray light from