8" F/8 RC Astrograph Telescope is not only perfect for Astrophotography but also for observing.
The RC has a concave hyperbolical primary mirror and a convex hyperbolical secondary mirror. The resulting image correction throughout the field as well as the sharpness on the optical axis are superior to typical Schmidt-Cassegrains or Newtonians. Both mirrors are ground and polished under pricision computer control to diffraction-limited or better surface accuracy.
 
Advantages of RC Telescopes compared to MAC and SCT
Aperture 8" / 203mm.......Focal Length 1600mm
f/8 is faster than a 8" SC or Mak
illuminated field is much bigger
you can attach 2" eyepieces and full size SLR/DSLR cameras without vignetting
two hyperboloidical mirrors with 96% reflectivity lead to a bright image
faster cool-down time and no dew problems because of open tube design without front correcting plate
enough back focus for all kinds of accessories like correctors and reducers
2" MONORAIL Focuser with better stability
Less dew problems against Schmidt Cassegrain or similar
fixed mirrors and 2" Crayford focuser with 1:10 dual speed transmission - no problems with mirror shift
A rotatable, machined dual-speed (10:1) Crayford focuser equipped with a sturdy linear-bearing provides precise focus adjustment without slippage or flexure with heavy astrophotography accessories attached
Features one dovetail finder scope bases.
8" RC f/8 Astrograph is designed for full illumination of the "35mm format" (24 x 36mm).
The GSO 8" RC astrograph (a telescope designed specifically for photographing comparatively wide areas of the sky) makes the coma-free imaging of true Ritchey-Chrétien imaging optics available to the DSLR and CCD astrophotographer at a price less than that of most CCD cameras. It is not designed for digiscoping through an eyepiece. Featuring premium low thermal expansion quartz mirrors rather than ordinary optical glass, this very economical 8” R-C makes you wonder just what those outrageously expensive R-Cs have that makes them cost so much.
Designed for exceptional imaging, the 8 inch RC provides the wide coma-free photographic field that DSLR and CCD astrophotographers crave, but can’t get from conventional reflectors and Schmidt-Cassegrains. Likewise, as a pure two-mirror system, the 8 RC 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 8” aperture that dwarfs the light gathering of most apo refractors.
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 8 inch RC astrograph can bring the world of professional DSLR/CCD deep space imaging to your backyard observatory at a remarkably affordable price.
 
Optical design
True Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors.
 
Optical specifications
8” aperture, 1625mm focal length, f/8 focal ratio.
 
Hyperboloid primary mirror
Made of low thermal expansion quartz, rather than the ordinary optical glass used by competitors. Ground and polished under precision computer control to diffraction-limited or better surface accuracy. 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 8RC primary mirror is fixed to eliminate both a catadioptric’s image shift and the primary mirror collimation requirements of a Newtonian reflector.
 
Hyperboloid secondary mirror
Made of low thermal expansion quartz, rather than ordinary optical glass. Ground and polished under precision computer control to diffraction-limited or better surface accuracy. Mounted in a four-vane spider and fully collimatable using simple standard Cassegrain reflector collimating techniques. Unlike complicated R-C designs that use motors to move the secondary mirror fore and aft to focus, the 8RC secondary mirror is fixed and focusing is done externally.
 
96% reflectivity enhanced aluminum coated optics
Both primary and secondary mirrors are coated with 96% reflectivity enhanced aluminum, overcoated with a layer of quartz for long life.
 
Steel optical tube
While not quite as resistant to temperature-related focus changes as its more expensive carbon fiber brother, the 9” o.d. x 18” long steel tube of the AT8RCS will require few, if any, focus adjustments during most imaging sessions.
 
Multiple internal light baffles
Computer optimized primary and secondary baffling. 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 provide truly dark sky backgrounds during imaging.