True Ritchey-Chrétien telescopes typically start at many thousands of pounds, putting them out of the reach of most astro imagers. This however is a true Ritchey-Chrétien astrograph optical design at a very affordable price. The Astro-Tech AT6RC makes the coma-free imaging of a true Ritchey-Chrétien optical system available to amateur astronomers using Deep Sky Imager-type cameras, Digital Cameras (DSLRs) various CCD cameras. It does it at a price less than that of a mid range CCD camera. Designed strictly for imaging, the Astro-Tech AT6RC provides the wide coma-free photographic field that astro-photographers need, but can’t get from conventional reflectors and Schmidt-Cassegrains. Likewise, as a pure two-mirror system without any lenses in the light path, the AT6RC is totally free from the spurious colour which affects imaging of all but the most costly apochromatic refractors, and it does it with an 6" aperture that equals or exceeds the light gathering of most APO refractors with a flat field.

AT6 RC Astrograph’s Optical System . . .

• Optical design: true Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors. Click here for more details on the RC Optical Design (new window)
• Aperture: 152mm 1370mm focal length, f9 focal ratio.
• Primary mirror: Made of BK-7 optical glass. 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 AT6RC primary mirror is fixed to eliminate image shift and focus changes.
• Secondary mirror: Made of BK-7 optical glass. Polished to 1-12th wave or better surface accuracy. Mounted in a four-vane spider - 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 AT6RC secondary mirror is fixed and focusing is done externally.
• Enhanced aluminium optical coatings: Both primary and secondary mirrors have enhanced aluminium mirror coatings, over coated with a protective layer of quartz for long life. Reflectivity is in the 96% range.
• Optical tube: Aluminium, 7.5" OD x 19.25" length, with die-cast and machined aluminium front and rear cells.
• Internal light baffles: Computer optimized primary and secondary baffling. Eight contrast-enhancing glare-stop baffles in the optical tube, multiple glare-stop micro baffles in the secondary mirror light shield, and four baffles in the primary mirror baffle tube provide truly dark sky backgrounds during imaging.
• Dual-speed Crayford focuser: The 2" non-Vignetting 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 micro fine focusing ratio. This provides exceptionally precise image control during critical CCD imaging. All focus knobs are ribbed, so they are easy to operate, even while wearing gloves or mittens in cold weather. Focuser drawtube travel is 40mm.
• Mounting dovetail: removable Vixen-style dovetail bar running the length of the underside of the optical tube.
• Finder scope dovetail: a Vixen-style finder scope 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 finder scope brackets as well as Red Dot type finders.
• Other accessories: A snap-in dust cap is standard.
• Two year warranty: As an expression of the confidence Astronomy Technologies has in the quality of their products, the Astro-Tech AT6RC is protected by a two-year limited warranty against flaws in materials and workmanship (shipping case excluded as it is considered a protective layer).