This Sky & Telescope Hot Product for 2010 has standard equipment premium features – like a high strength/low thermal expansion carbon fiber body instead of rolled steel, low expansion quartz mirrors instead of ordinary glass, 99% reflective dielectric mirror coatings instead of ordinary aluminum, and two dovetail mounting rails instead of one – that competitors simply don’t offer.
The Ritchey-Chrétien optical design is used in virtually every recent large mega-million dollar professional observatory telescope – including the Hubble Space Telescope. But the Astro-Tech AT8RC doesn’t cost mega-millions, or even mega-thousands. The Astro-Tech AT8RC makes the coma-free imaging of a true Ritchey-Chrétien optical system available at a price lower than most CCD cameras.
The 8” f/8 Astro-Tech AT8RC Astrograph is a true Ritchey-Chrétien Cassegrain-type optical system, with hyperbolic primary and secondary mirrors made of low thermal expansion quartz, rather than the simple optical glass used by competitors. Both mirrors have non-tarnishing state-of-the-art dielectric mirror coatings with a full 99% reflectivity, substantially higher than the 88% to 94% reflectivity of competitors’ conventional aluminum coatings.
The optical tube is made of light weight/high strength carbon fiber-reinforced composite with extremely low thermal expansion characteristics. This reduces the possibility of temperature-related focus changes that can occur with competitors’ rolled steel tubes. There are ten contrast-enhancing glare-stop baffles in the optical tube; multiple glare-stop microbaffles in the secondary mirror light shield; and five baffles in the primary mirror baffle tube to provide truly dark sky backgrounds during imaging.
Two threaded extension tubes are provided to install singly or in combination between the AT8RC rear cell and the focuser. These provide a flex-free solid metal extension that changes the distance between the focuser and the rear cell to accommodate the varying back-focus requirements of DSLR-type cameras versus CCD cameras. Additional optional threaded extension tubes are available to fine-tune the back focus as needed, as well as optional Astro-Tech 2” compression ring extension tubes that fit into the focuser drawtube.
Two non-marring compression ring accessory holders are supplied, one 2” and one 1.25”. A Vixen-style finderscope shoe 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.
Two dovetail rails are provided. One is a Losmandy-style “D-plate” dovetail rail that runs the full length of the underside of the optical tube, for installing the AT8RC on a Losmandy-style equatorial mount. The second is a Vixen-style dovetail rail that runs the full length of the top of the tube. This can be used for installing a photoguide ring set, piggyback camera adapter, or any other accessory that attaches to a scope by means of Vixen-style dovetail adapters. If the AT8RC is rotated 180°, it will bring the Vixen-style rail to the bottom of the tube so it can be used to install the AT8RC on a Vixen-style equatorial mount. Providing two dovetail rails on the Astro-Tech AT8RC does not limit your choice of mounts or accessory mounting options, as can happen with competitive scopes that have only one mounting rail.
- Focal Length: 1625mm
- Focal Ratio: f/8
- Resolution: 0.57 arc seconds
- Aperture: 8"
- 8” f/8 true Ritchey-Chrétien hyperbolic mirror optical design
- Low thermal expansion quartz primary and secondary mirrors, not the ordinary optical glass used by competitors
- 99% reflectivity non-tarnishing dielectric mirror coatings, not the lower reflectivity aluminum coatings used by competitors
- High strength/low thermal expansion carbon fiber optical tube, not the rolled steel used by competitors
- Ten contrast-enhancing main tube light baffles
- Dual-speed 2” Crayford focuser
- 2” and 1.25” compression ring accessory holders
- Finderscope mounting shoe
- Two dovetail rails – one Vixen-style and one Losmandy-style “D-plate” – not simply the single Vixen-style dovetail