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Review Summary
The Optical Design of the Orion 8" Ritchey-Chretien Astrograph allows you to capture spectacular, detailed images of deep-sky objects like never before. In contrast to conventional Newtonian reflector and Schmidt-Cassegrain designs that are susceptible to coma away from the center of the field, the Ritchey-Chretien utilizes hyperbolic primary and secondary mirrors to achieve superb flat-field images that are truly coma-free.
In the 8" model, the mirrors are made of BK-7 optical glass with enhanced aluminum 94% - 96% reflectivity coatings, to provide diffraction-limited performance. Since there are no lenses involved, images are also free from chromatic aberration, which affects all but the finest, most expensive apochromatic refractors. The Orion 8" Ritchey-Chretien Astrograph Telescope is ideal for use with small CCD-chip cameras such as the award-winning StarShoot line, as well as large-format CCD and DSLR cameras, for deep-sky and solar system astrophotography.
The telescope's wide, fully illuminated flat field produces pinpoint star clarity all the way to the edge of the camera's sensor. The Orion 8" Ritchey-Chretien Astrograph features a machined, dual-speed (10:1) Crayford-style focuser with an engraved millimeter scale on the drawtube. One 2-inch and two 1-inch extension rings are included for adjusting the focus position for various cameras. Focus travel readily accommodates popular imaging accessories.
The secondary mirror is precisely center-marked to facilitate collimation. The 21-inch enameled steel optical tube weighs only 15.8 lbs. and features a dovetail mounting bar underneath, for trouble-free setup on medium or large-sized Orion equatorial mounts. The inside of the optical tube is fortified with ten computer-positioned light baffles and the primary mirror baffle tube and secondary mirror light shield are also highly baffled to ensure maximum image contrast.
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