Astro-Tech 12" f/8 Ritchey-Chrétien optical tube


Availability: More on the way

The 12" Astro-Tech AT12RC Ritchey-Chrétien astrograph is a large aperture true Ritchey-Chrétien astrograph, an astro-imager's dream, a Sky & Telescope Hot Product for 2011, and - at a price thousands below competitive scopes - the first reasonably-priced 12" true R-C available.
Our Product #: AT12RC
Astro-Tech Product #: AT12RC
Recommended Accessories

Product Description

Developed by Astro-Tech to make large-aperture/large-format CCD imaging affordable for the dedicated amateur astronomer and educational institution, the 12" Astro-Tech AT12RC is priced thousands of dollars less one competitor's 10" R-C! The Astro-Tech AT12RC is truly the first affordable 12" true Ritchey-Chrétien astrograph.

This Astro-Tech AT12RC Ritchey-Chrétien astrograph has:

• 12" f/8 true Ritchey-Chrétien hyperbolic mirror optical design
• low thermal expansion quartz primary and secondary mirrors
• center spotted secondary mirror
• three built-in cooling fans in rear cell
• 3" Crayford-style focuser with 2" and 1.25" compression ring adapters
• two 2" focuser extension rings to fine-tune the back focus of your focuser
• rolled steel tube with cast and machined aluminum front and cell
• split hinged tube rings with two Losmandy-style "D-plate" dovetail rails
• mounting bracket for optional finder

The 12" Astro-Tech AT12RC is the first 12" true Ritchey-Chrétien astrograph available at a reasonable price. It joins the line-up of other Astro-Tech Ritchey-Chrétien astrographs that have previously been honored by Sky & Telescope (the original Astro-Tech 6" R-C was named a Hot product for 2009 and the Astro-Tech 8" and 10" R-Cs were named Hot Products for 2010).

And we are serious when we say the 12" aperture AT12RC is "reasonably priced." The Astro-Tech AT12RC is priced many thousands of dollars less than one competitive 12.5" R-C, and still thousands less than another manufacturer's smaller 10" R-C. As Sky & Telescope pointed out in their Hot Product citation in their January 2010 issue, "Ritchey-Chrétien reflectors are highly regarded among today's elite astrophotographers, and premium instruments often carry price tags starting at about $1,000 per inch of aperture. So it's the best kind of "sticker shock" to see the prices for Astro-Tech's Ritchey-Chrétiens." (The AT12RC is priced at only a third of that per inch of aperture figure.)

The Ritchey-Chrétien optical design is used in virtually every recent large mega-million dollar professional observatory telescope - including the Hubble Space Telescope. The Astro-Tech AT12RC astrograph makes the coma-free imaging of true Ritchey-Chrétien imaging optics available to the DSLR and large format CCD astrophotographer at a price less than that of many large format CCD cameras by themselves and even less than some DSLR camera bodies. Featuring premium low thermal expansion quartz mirrors, rather than aluminized Pyrex glass mirrors, this reasonably-priced 12" Astro-Tech R-C makes you wonder just what competitive high-price R-Cs have that makes them cost so much more.

Designed for exceptional imaging, the Astro-Tech AT12RC provides the coma-free photographic field that large format CCD astrophotographers crave, but can't get from conventional reflectors and Schmidt-Cassegrains. Likewise, as a pure two-mirror system, the AT12RC has a wide spectral response and 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 12" aperture that dwarfs the light gathering of virtually every commercially-available apo refractor.

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 12" Sky & Telescope Hot Product for 2011 Astro-Tech AT12RC astrograph can bring the world of professional DSLR/CCD deep space imaging to your backyard observatory at a truly affordable price.

Features of this Astro-Tech AT12RC Astrograph . . .

Optical design: true Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors. The 288mm of available back focus allows for the use of long CCD equipment trains.

Optical specifications: 12" aperture, 2432mm focal length, f/8 focal ratio.

Hyperboloid primary mirror: Made of low thermal expansion quartz. Ground and polished under precision computer control. Unlike catadioptric designs (SCTs, Maksutovs, etc.) 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 AT12RC primary mirror is fixed to eliminate both a catadioptric's image shift and the frequent primary mirror collimation requirements of a Newtonian reflector. Focusing is done by means of an optional external focuser, discussed below. Primary mirror collimation is pre-set at the factory, but can be adjusted if needed using three traditional push/pull locking adjustment screw sets.

Hyperboloid secondary mirror: Made of low thermal expansion quartz, rather than Pyrex. Ground and polished under precision computer control. Mounted in a CNC-machined four-vane spider and fully collimatable using simple standard Cassegrain reflector collimating techniques. The secondary mirror is precisely center-spotted to make collimation easier. Unlike complicated R-C designs that use motors to move the secondary mirror fore and aft to focus, the AT12RC secondary mirror is fixed and focusing is done externally by means of an optional external focuser, discussed below.

Sky & Telescope said that the Astro-Tech R-C's fixed primary and secondary mirrors "eliminate image shift, which has been the bane of Cassegrain scopes with moving-mirror focusing systems . . . It also keeps the effective focal length of the system constant, and the infinity focal point remains at a fixed point outside of the telescope, neither of which is the case with moving-mirror systems that change the separation between a Cassegrain's primary and secondary mirrors."

3" focuser: A 3" Crayford-style focuser with a 2" compression ring accessory holder and a separate 1.25" compression ring adapter is standard equipment for use with light imaging trains (such as a DSLR body by itself).

This linear bearing focuser has a polished stainless steel drive rail that runs the length of the drawtube, rather than having the stainless steel drive shaft simply press directly on (and wear) the aluminum drawtube as with conventional Crayford focusers. The drive rail rides in a self-lubricating track that supports the drive rail and its attached drawtube over most of their length at all times, rather than by a conventional Crayford focuser's two sets of small contact area roller bearings. This system distributes the drive force evenly over the entire drawtube, without concentrating it on a few small contact points. The result is less potential drawtube flexure and no wear (much less uneven wear) on the drawtube.

The precision-made 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 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. There is a focusing scale, in inches and mm, on the top of the drawtube.

The robust construction of the supplied 3" focuser is designed primarily for imaging with a DSLR body. If you plan on imaging with a heavy CCD imaging train, however, you might want to substitute a heavy-duty rack and pinion focuser (from Feather Touch or Moonlite, for example) for additional stability and precision. One popular choice is the dual-speed 3" diameter 1.5" travel Feather Touch #3015 rack and pinion focuser, available from your Astro-Tech dealer.

The rear cell of the AT12RC has a male 117m x 1mm pitch threaded port for attaching a focuser. The standard Feather Touch 3" diameter 1.5" travel focuser normally comes with a 109mm threaded collar for connecting to a scope. However, in its #3015 configuration (Feather Touch part #FTF3015B-A), it requires an optional #M117x1 Feather Touch adapter to be used with the AT12RC. The #3015 focuser (without 109mm collar) slips into this adapter and is held in place by three large brass Delrin-tipped retaining knobs. Only focusers with a maximum 1.5" drawtube travel, such as the Feather Touch #3015, are recommended for use with the Astro-Tech AT12RC 12" Ritchey-Chrétien. For brands of focusers other than Feather Touch, such as MoonLite, contact the focuser manufacturer for an adapter to fit the 117mm x 1mm port on the rear of the scope.

To fine-tune the 288mm back focus of the AT12RC to the requirements of your camera and equipment train, two threaded extension rings (each 2" in length) are provided to thread singly or in combination between the 117mm port on the AT12RC rear cell and the focuser of your choice. These provide a flex-free solid metal extension that changes the distance between your chosen focuser and the rear cell. This lets you accommodate the varying back-focus requirements of DSLR-type camera imaging versus long equipment train CCD imaging. Each 2" x 117mm diameter threaded ring weighs 14.4 ounces.

Cooling fans: To allow the AT12RC to reach ambient temperatures more quickly for optimum imaging performance, there are three small low vibration/high CFM primary mirror cooling fans built into the rear cell. The high speed DC fans are powered by a standard equipment battery pack that plugs into a jack on the rear cell. The battery pack uses eight user-supplied AA batteries. An optional external DC power supply, such as a rechargeable 12VDC battery pack can also be used to power the fans.

Split rings and two dovetail mounting rails: Dual split hinged mounting rings, joined by two 14" Losmandy-style "D-plate" dovetail rails bolted to the rings, are provided for installing the AT12RC on an equatorial mount, as well as for mounting optional accessories (such as rings for a photoguide scope) on top. The rings are positioned so that one rail is underneath the 14.3" diameter by 34" long (without focuser) optical tube for installing the AT12RC directly on a suitable payload capacity equatorial mount. The second rail, 180° away from the first, will then be on top of the tube for installing a photoguide scope or any other accessory that attaches to a scope by means of Losmandy-style "D-plate" dovetail adapters. The undersides of the dovetails have been hollowed out to lighten their weight without compromising their strength. The rings and dovetails have a combined weight of 7.8 pounds (3.55 kg).

Finderscope dovetail: A Vixen-style finderscope bracket dovetail base is installed on the upper left side of the optical tube rear cell. 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.

Tech Details

Aperture 12"
Binary and Star Cluster Observation No
Focal Length 2432mm
Focal Ratio f/8
Galaxy and Nebula Observation No
Heaviest Single Component 41.5 lbs.
Lunar Observation No
Weight 49.3 lbs.
Planetary Observation No
Resolution 0.38 arc seconds
Telescope Type Ritchey-Chrétien
Warranty 1 year
Back Focus 11.33 (288mm) from rear cell


Review by:
The Astro Tech 12 RC has become my favorite scope in the observatory. I couldn't see spending two or three times the amount. Any improvement there may be for double the money, I wouldn't be able to notice anyhow. The focuser is first-rate and the fit and finish is superb. Scopes may come and scopes may go but the AT12RC has it's forever home (side by side with my AT10INT) at Backyard Observatories. (Posted on 1/10/2019)
Review by:
Un amigo tiene este tubo junto con una montura CGX-L de 75 lb, y trabaja espectacular! las capturas resultantes son excelente, y su luminosidad es muy buena para ser óptica RC, muy recomendado :) (Posted on 10/13/2018)
Review by:
I've had this scope for about 5 years now. It's a solid piece of gear. For this price there really isn't anything close in terms of reach and value.

You will need to learn how to collimate this scope, in a serious way. Learn about it!

On retrospect, i would have spent a little more and gotten carbon fiber. This is a REALLY have scope to carry around. (Posted on 10/7/2018)
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Supplied Accessories

• two 2" focuser extension rings to fine-tune the back focus of your optional focuser
• rolled steel tube with cast and machined aluminum front and cell
• split hinged tube rings with two Losmandy-style "D-plate" dovetail rails 
• mounting bracket for optional finder