Ritchey-Chrétien astrographs

More Information  · Recommended Accessories  · Images of Some Features Price $795.00 Shipping $20.00 List Price $1,295.00 Focal Length 1370mm Focal Ratio f/9 Resolution 0.76 arc seconds Aperture 6" Net Weight 12.9 lbs. Warranty 2 years

   Astro-Tech Ritchey-Chrétien optics

This AT6RC Ritchey-Chrétien photo/visual scope has: • 6" f/9 true Ritchey-Chrétien hyperbolic mirror optical design • 1/12th wave or better BK-7 mirrors • enhanced aluminum optical coatings • dual-speed Crayford focuser • 2" and 1.25" compression ring accessory holders • Vixen-style dovetail plate

New production economies let us pass on a substantially lower price to you on this unique 6" Ritchey-Chrétien scope! Originally introduced at $1295 – and named a Sky & Tel Hot Product for 2009 at that price – the Astro-Tech 6" R-C is an even hotter product at its new $795 price!

    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 AT6RC, an incredibly affordable Ritchey-Chrétien photo/visual optical system that virtually all astronomers can afford!

    The Astro-Tech AT6RC makes coma-free Ritchey-Chrétien optics available to amateur astronomers at a price within reach and reason for nearly everyone. The AT6RC is designed primarily for coma-free imaging using webcams, Deep Sky Imager-type cameras, and DSLRs. Featuring a true Ritchey-Chrétien optical system, this very economical 6" 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 AT6RC provides the wide coma-free photographic field that astrophotographers crave, but can’t get from conventional reflectors and Schmidt-Cassegrains. Likewise, as a pure two-mirror system, the AT6RC 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 6" aperture that equals or exceeds the light gathering of most apo refractors.

Visual observing is also very possible with the AT6RC. The scope’s 2" 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.

The compact size and light weight of the AT6RC makes it easy for you to mount it on any mid-range equatorial mount by itself or piggyback it on your existing larger scope for imaging.

    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 AT6RC can bring the world of professional deep space imaging to your backyard observatory at a truly affordable price.

This Scope’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: 6", 1370mm focal length, f/9 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 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 AT6RC secondary mirror is fixed and focusing is done externally.

• Enhanced aluminum optical coatings: Both primary and secondary mirrors have enhanced aluminum mirror coatings, overcoated with a protective layer of quartz for long life. Reflectivity is in the 96% range, the same as those $10,000+ R-C scopes.

• Optical tube: Painted rolled steel, 7.5" o.d. x 19.25" long, with die-cast and machined aluminum 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 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 Crayford focuser: The 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 microfine 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 travel: Focuser drawtube travel is 40mm. 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 webcam/Deep Sky Imager-type camera imaging versus DSLR-type camera imaging. While it is possible to use SBIG ST-7/8/9/10/2000-type CCD cameras with the AT6RC, these cameras are generally not recommended. The weight of an SBIG camera and the color filter wheel typically used with it may cause the focuser drawtube to tilt slightly when fully extended, affecting the focus. Adding an optional Feather Touch focuser will eliminate any such potential problem, although at significant additional cost.

• 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" eyepiece holder on the eyepiece holder rotation mechanism, the 1.25" adapter also uses a non-marring soft brass compression ring.

• Mounting dovetail: removable Vixen-style dovetail bar running 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.

• 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).