Detailed information about this product's features  Astro-Tech Ritchey-Chrétien optics
This AT8RC Ritchey-Chrétien photo/visual scope has:
• 8" f/8 true Ritchey-Chrétien hyperbolic mirror optical design
• low thermal expansion quartz primary and secondary mirrors
• 99% reflectivity non-tarnishing dielectric mirror coatings
• high strength/low thermal expansion carbon fiber optical tube
• genuine Feather Touch dual-speed Crayford focuser
• 2" and 1.25" compression ring eyepiece holders
• Losmandy-style “D-plate" dovetail
New production economies let us pass on a substantially lower price to you on this 8" Ritchey-Chrétien scope! Originally introduced at $2995, the Astro-Tech 8" R-C is now available for only $2495!
The Ritchey-Chrétien optical design is used in virtually every recent large mega-million dollar professional observatory telescope – including the Hubble Space Telescope. And more “affordable" true coma-free Ritchey-Chrétien optical systems made for schools and individuals by commercial R-C manufacturers typically come only in large apertures and start at well over $10,000. Their size and cost put them out of the reach of most amateur astronomers. At least, true Ritchey-Chrétiens used to start at $10,000 and up.
Introducing the Astro-Tech AT8RC, the first affordable large Ritchey-Chrétien astrograph!
The Astro-Tech AT8RC makes the coma-free imaging of a true Ritchey-Chrétien optical system available to the DSLR and CCD astrophotographer at a price less than that of most 35mm-format CCD cameras. Featuring first-quality dielectric mirror coatings (something even the $10,000+ R-Cs typically don’t have), premium low thermal expansion quartz mirrors rather than ordinary optical glass, and a high strength/low thermal expansion carbon fiber optical tube, this economical 8" Astro-Tech R-C makes you wonder just what those $10,000+ R-Cs have that makes them cost so much.
Designed primarily for exceptional imaging, the Astro-Tech AT8RC provides the wide coma-free photographic field that 35mm film and 35mm-format CCD astrophotographers crave, but can’t get from conventional reflectors and Schmidt-Cassegrains. Likewise, as a pure two-mirror system, the AT8RC is totally free from the spurious color that affects the imaging of all but the most costly apochromatic refractors, and it does it with an 8" aperture that dwarfs the light gathering of most apo refractors.
Visual observing is also very possible with the AT8RC. The scope’s 2" Feather Touch Crayford focuser will accept both 1.25" and 2" star diagonals. Contrast may be slightly lower than with a conventional reflector, due to the somewhat larger secondary obstruction inherent in the R-C design. However, beta-testers of the prototype at star parties were highly impressed by the visual image quality and felt that the coma-free images more than outweighed any possible slight loss of contrast.
If serious astrophotography is your goal, but the price of most true Ritchey-Chrétien optics has been keeping you from the optical design most modern professional observatories and the Hubble Space Telescope use for their imaging, your wait is over. The Astro-Tech AT8RC can bring the world of professional deep space imaging to your backyard observatory at a truly affordable price.
This Astrograph’s Optical System . . . - Optical design: true Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors. For more details, click on the “optics" icon above.
- Aperture: 8", 1625mm focal length, f/8 focal ratio.
- Primary mirror: Made of low thermal expansion quartz. Polished to 1/12th wave or better surface accuracy. Unlike designs that move the primary mirror fore and aft in the optical tube to focus (which can lead to image shift as the mirror position changes) the AT8RC primary mirror is fixed to eliminate image shift and focus changes.
- Secondary mirror: Made of low thermal expansion quartz. Polished to 1/12th wave or better surface accuracy. Mounted in a four-vane spider and fully collimatable using simple standard Schmidt-Cassegrain collimating techniques. Unlike complicated R-C designs that use motors to move the secondary mirror fore and aft to focus, the AT8RC secondary mirror is fixed and focusing is done externally.
- Dielectric coated optics: Both primary and secondary mirrors have non-tarnishing state-of-the-art dielectric mirror coatings. These have a full 99% reflectivity for the brightest possible images. This is substantially higher than the 88% reflectivity of conventional aluminum coatings or the 94-96% reflectivity of enhanced aluminum coatings.
- Optical tube: Made of light weight/high strength woven carbon fiber-reinforced composite material with extremely low thermal expansion characteristics to reduce the possibility of temperature-related focus changes. Die-cast and machined aluminum front and rear cells. The 9" o.d. x 20.25" long carbon fiber tube is virtually indestructible. The use of a carbon fiber composite reduces the weight of the optical tube with no loss of strength or rigidity compared to an aluminum tube. Carbon fiber composites are so strong that the new $200,000,000 Boeing 787 Dreamliner passenger jet will use a wing and fuselage made entirely out of carbon fiber. Because of the use of a carbon fiber optical tube, the weight of this 8" R-C is only a little more than two pounds heavier than the steel tube 6" Astro-Tech R-C.
- Internal light baffles: Computer optimized primary and secondary baffling. Eight contrast-enhancing glare-stop baffles in the optical tube, multiple glare-stop microbaffles in the secondary mirror light shield, and four baffles in the primary mirror baffle tube provide truly dark sky backgrounds during imaging.
- Dual-speed microfine Feather Touch Crayford focuser: The precision-made non-vignetting focuser is a genuine Feather Touch from Starlight Instruments, a company known world-wide for making the finest and most reliable focusers available to the amateur astronomer. The focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with a 10:1 reduction gear microfine focusing ratio. This provides exceptionally precise image control during critical 35mm or CCD imaging. All focus knobs are ribbed, so they are easy to operate, even while wearing gloves or mittens in cold weather. Multiple internal baffles in the focuser drawtube assure high contrast.
- Compression ring accessory holders: The focuser drawtube ends in a 2" accessory holder that uses a non-marring soft brass compression ring to hold 2" imaging accessories in place. The compression ring won’t scratch the barrel of your accessories as an ordinary thumbscrew can. Also supplied is a 1.25" accessory holder that slips into the 2" compression ring holder to let you use 1.25" imaging accessories. Like the 2" accessory holder on the drawtube, the 1.25" adapter also uses a non-marring soft brass compression ring. The 2" accessory holder can be removed from the drawtube to allow the installation of custom A-P type photo accessories available directly from Starlight Instruments.
- Extension tubes: Two extension tubes are provided to let you change the position of the focuser relative to the rear cell. This lets you accommodate the varying back-focus requirements of visual observing with eyepiece and diagonal versus DSLR-type camera imaging versus CCD imaging.
- Mounting dovetail: a removable Losmandy-style “D-plate" dovetail runs the length of the underside of the optical tube.
- Finderscope dovetail: a Vixen-style finderscope bracket dovetail base is installed on the upper left side of the optical tube. It can easily be removed if not needed. It will accept Vixen-style finderscope brackets as well as red dot-type finders, such as the Astro-Tech #ATF.
- Other accessories: A snap-in dust cap is standard.
- Shipping/storage case: The scope comes in a protective locking hard case with carry handle.
Astro-Tech is one of the very few manufacturers to provide a case at no charge for protection during shipping and as a storage convenience when the scope is not in use. Unfortunately, FedEx, UPS, and the Postal Service are very good at treating packages roughly. Occasionally, your scope can arrive in perfect condition, but with the walls of the shipping case dented in transit from rough handling, or the aluminum frame sprung, rendering the appearance of the case less than pristine. Damage to the shipping case in such instances is not covered by warranty.
- Two year warranty: As an expression of the confidence Astronomy Technologies has in the quality of their products, the Astro-Tech AT8RC is protected by a two-year limited warranty against flaws in materials and workmanship (shipping case excluded).
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