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Orion - 8 " f/8 Ritchey Cretien Optical Tube Assembly

Model#: 8958

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Manufactured by: Orion

Orion - 8 " f/8 Ritchey Cretien Optical Tube Assembly


- Ritchey-Chretien optical design produces superb flat-field, coma-free images that are superior to those achievable with conventional reflector or Schmidt-Cassegrain telescopes
- One of the most compact Ritchey-Chretien astrographs available, at a breakthrough low price of less than $1200! Until now, RCs typically cost upwards of $10,000
- Ideal for use with both small and large-format CCD cameras and DSLRs; provides a wide, fully illuminated field and pinpoint star clarity out to the edge of the camera's sensor
- Optical tube has ten computer-positioned baffles to ensure maximum contrast; primary mirror tube has four internal baffles; secondary mirror light shield has internal glare thread baffles
- Compact, lightweight optical tube is ideally suited for use on medium and large-sized equatorial mounts

As any prolific astrophotographer will tell you, the more light you can gather, the better your astrophotos will turn out. Combine light-gathering prowess with a compact design and an affordable price, and you're likely to end up with our new 8" f/8 Ritchey-Chretien Astrograph. As a leading supplier of affordable imaging equipment and solutions for amateur astronomers, Orion is proud to introduce this highly regarded telescope design used by advanced astrophotographers and professional observatories worldwide - and even by the Hubble Space Telescope!

Previously available only in larger apertures that cost thousands more, the outstanding optical design of the Orion 8" Ritchey-Chretien Astrograph will allow 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 our 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 our 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.

Without a doubt, our 8" Ritchey-Chretien Astrograph brings advanced astrophotography performance into the realm of affordability for most amateur astronomers. More affordable than comparably sized apochromatic refractors and without the coma that afflicts Newtonian reflectors, the Orion 8" f/8 Ritchey-Chretien Astrograph Telescope will take your astrophotography to new heights! One-year limited warranty.

Product Specifications:
Use Astronomy & terrestrial
User level Advanced
Optical design Ritchey-Chretien
Optical diameter 200mm
Focal length 1600mm
Focal ratio f/8.0
Optics type Hyperbolic
Resolving power 0.58arc-sec
Lowest useful magnification 29x
Highest useful magnification 300x
Limiting stellar magnitude 14.2
Optical quality Diffraction limited
Finder scope None
Focuser 2" Crayford
Secondary mirror obstruction 93mm
Secondary mirror obstruction by diameter 46%
Secondary mirror obstruction by area 22%
Mount style Optical Tube without Mount
Astro-imaging capability Lunar, planetary & long exposure
Tube material Aluminum
Length of optical tube 21.8 in.
Weight, optical tube 15.8 lbs.
Additional included accessories Two 1" and one 2" removable extension tubes
Other features Knife-edge baffling
Warranty One year

Included Items:
One two inch long extension ring
Two one inch long extension rings
One 1.25 inch eyepiece adapter insert
Starry Night Special Edition Software

Additional Information

Name Orion - 8 " f/8 Ritchey Cretien Optical Tube Assembly
Manufacturer Orion
Model 8958