Astro-Tech AT6CC 6" f/12 Classical Cassegrain

In 2008 we began to work with GSO to develop a line of RC scopes. They have been quite successful over the past decade and have proven to be fantastic instruments. In the Summer of 2017 we began to think about what could be next. We decided to take the expertise of GSO and have them apply it to a telescope design that has been revered for years by astronomical observers….the Classical Cassegrain.

The Classical Cassegrain is known for its outstanding views at the eyepiece, giving APO refractor like views without the expense associated with a large triplet refractor. The parabolic primary mirror, and hyperbolic secondary mirror combine to make the secret sauce that gives this design its optical advantage and prevents spherical aberration.

Compared to large refractrors the Astro-Tech AT6CC is not only incredibly affordable, but it is also incredible transportable and light. You will not need a giant mount to take your AT6CC out to observe as the OTA weighs in at around 13 pounds.

The AT6CC is designed primarily for visual use, but astro-photography is well within its reach. Planetary, lunar, really anything you can snap a photo of. Keep in mind however, the Classical Cassegrain design will have coma like a standard reflector due to its parabolic mirror so widefield photography is not its strong point.

Optical design: true Classical Cassegrain two-mirror optics, with parabolic primary and hyperbolic secondary mirrors. 6" aperture, 1836mm focal length, f/12 focal ratio.
Parabolic primary mirror:  Polished to diffraction-limited or better surface accuracy. Unlike catadioptric designs (SCTs, Maksutovs, etc.) that move the primary mirror to focus (which can lead to image shift as the mirror moves), the AT6CC mirror is fixed to eliminate potential image shift. The fixed primary mirror also eliminates the frequent primary mirror collimation requirements of a Newtonian reflector.

Hyperboloid secondary mirror:  Polished to diffraction-limited or better surface accuracy. Mounted in a four-vane spider and fully collimatable.
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 the larger multi-thousand dollar R-C scopes.

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: A 2" Crayford focuser is threaded onto the 90mm x 1mm pitch rear cell of the AT6CC. 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. 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.

Other accessories: A snap-in dust cap is standard.