TrevorW
22-04-2009, 02:12 PM
Information and reviews on this scope have been scarce eveeryone so far that has brought one has had bad weather to endure however this information from Astronomics site may help.
This is the GSO scope just different badging (by the way Made in Taiwan)
This Astro-Tech AT8RC Ritchey-Chrétien astrograph has:
• 8" f/8 true Ritchey-Chrétien hyperbolic mirror optical design
• low thermal expansion quartz primary and secondary mirrors, not ordinary optical glass
• 99% reflectivity non-tarnishing dielectric mirror coatings, not lower reflectivity aluminum coatings
• high strength/low thermal expansion carbon fiber optical tube, not merely rolled steel
• ten contrast-enhancing main tube light baffles, not eight
• dual-speed Crayford focuser
• 2" and 1.25" compression ring eyepiece holders
• two dovetail rails – one Vixen-style and one Losmandy-style “D-plate" – not simply a single Vixen-style dovetail
• an optional reducer/field flattener is available
Features of this Astro-Tech AT8RC Astrograph . . .
Optical design: true Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors.
Aperture: 8", 1625mm focal length, f/8 focal ratio.
Hyperboloid primary mirror: Made of low thermal expansion quartz, rather than simple optical glass. Ground and polished under precision computer control. 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 AT8RC primary mirror is fixed to eliminate image shift and focus changes.
Hyperboloid secondary mirror: Made of low thermal expansion quartz, rather than simple optical glass. Ground and polished under precision computer control. 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 AT8RC secondary mirror is fixed and focusing is done externally.
99% reflectivity dielectric coated optics: Both primary and secondary mirrors have non-tarnishing state-of-the-art dielectric mirror coatings. These have a full 99% reflectivity for the brightest possible images. This is substantially higher than the 88% reflectivity of conventional aluminum coatings or the 94-96% reflectivity of enhanced aluminum coatings.
Carbon fiber optical tube: Made of light weight/high strength woven carbon fiber-reinforced composite material with extremely low thermal expansion characteristics to reduce the possibility of temperature-related focus changes that can occur with lesser steel tube systems. Die-cast and machined aluminum front and rear cells. The 9" o.d. x 18" long carbon fiber tube is virtually indestructible. The use of a carbon fiber composite reduces the weight of the optical tube with no loss of strength or rigidity compared to an aluminum tube. Because of the use of a carbon fiber optical tube, the weight of this 8" R-C is only a little more than two pounds heavier than the steel tube 6" Astro-Tech R-C.
Multiple internal light baffles: Computer optimized primary and secondary baffling. Ten contrast-enhancing glare-stop baffles in the optical tube, rather than eight; 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.
Dual-speed Crayford focuser: A 2" Crayford focuser is threaded onto the 90mm x 1mm pitch rear cell of the AT8RC. 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.
The weight of very heavy equipment trains (camera, plus filter wheel, plus temperature-compensated electric focuser, etc.) may cause the focuser drawtube to tilt slightly when fully extended, affecting the focus. Two threaded extension tubes are provided to install singly or in combination between the AT8RC rear cell and the focuser. These provide a flex-free solid metal extension that changes the distance between the focuser and the rear cell. This lets you accommodate the varying back-focus requirements of visual observing with eyepiece and diagonal versus DSLR-type camera imaging versus CCD imaging, while minimizing the need to extend the focuser drawtube. Additional optional threaded extension tubes are available to fine-tune the back focus as needed, as well as optional Astro-Tech 2" compression ring extension tubes that fit into the focuser drawtube.
For exceptionally long and heavy imaging equipment trains, the standard Crayford focuser can be user-replaced by an optional Feather Touch focuser from Starlight Instruments. This requires a 90mm x 1mm pitch rear cell thread to Feather Touch adapter available directly from Starlight Instruments.
Two 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" accessory holder on the drawtube, the 1.25" adapter also uses a non-marring soft brass compression ring.
Two dovetail mounting rails: Two dovetail rails are provided for installing the AT8RC on an equatorial mount, as well as for mounting optional accessories (such as a photoguide scope) on top of the AT8RC. One is a Losmandy-style “D-plate" dovetail rail that runs the full length of the underside of the optical tube, for installing the AT8RC on a Losmandy-style equatorial mount. The second is a Vixen-style dovetail rail that runs the full length of the top of the tube. This can be used for installing a photoguide ring set, piggyback camera adapter, or any other accessory that attaches to a scope by means of Vixen-style dovetail adapters. If the AT8RC is rotated 180°, it will bring the Vixen-style rail to the bottom of the tube so it can be used to install the AT8RC on a Vixen-style equatorial mount. Providing two dovetail rails on the Astro-Tech AT8RC does not limit your choice of mounts or accessory mounting options, as can happen with similar scopes provided with only one mounting rail.
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 AT8RC is protected by a two-year limited warranty against flaws in materials and workmanship.
Fully multicoated quartz and BK7 mirrors: The primary mirror of the 6” Astro-Tech is first-quality BK7 optical glass, while the 8” and larger Astro-Tech RCs use primary mirrors of low thermal expansion quartz for maximum focus stability during long exposure imaging sessions. Both 6” R-C mirrors are vacuum-coated with enhanced aluminum for high reflectivity and overcoated with a durable layer of silicon monoxide (quartz) for long life. The 8” and larger mirrors are dielectric coated for long life and reflectivity approaching 99%+.
Computer designed and fabricated optics: To keep the cost of each Astro-Tech RC so reasonable when compared to competitive RC scopes, the computer-optimized Astro-Tech hyperboloid mirrors are automatically ground and finished to very high tolerances using custom-made computerized mirror grinding machines. This precision computer control guarantees an exact repeatability of figure from mirror to mirror that is difficult to achieve using more costly conventional hand figuring. After grinding and polishing, each mirror is individually tested using a Zygo interferometer to assure that it meets or exceeds its specified surface accuracy.
Frill-free design: To further keep its cost reasonable, an Astro-Tech RC does away with most of the bells and whistles found on competitive scopes that add little to their performance (but much to their cost). For example, Astro-Tech front and rear cells are first die-cast, then CNC machine-finished, rather than completely CNC machined from raw stock at considerably greater expense but no significant improvement in performance as is the case with other RCs. Glare stops in the optical tube are a molded insert, rather than machined aluminum, resulting in a significant savings in cost at no appreciable difference in performance. The Astro-Tech scopes use an external manual dual-speed Crayford focuser, rather than the considerably more complicated and much more costly motorized movable secondary mirror system that other manufacturers use for focusing. The result of the Astro-Tech no-frills approach is genuine Ritchey-Chrétien wide-field performance at a fraction the cost of other commercial RC systems. While the mechanical bells and whistles may be limited in an Astro-Tech RC, an Astro-Tech scope still has the high precision flat field/coma-free true Ritchey-Chrétien optics that are the most important reason for buying an RC scope.
This is the GSO scope just different badging (by the way Made in Taiwan)
This Astro-Tech AT8RC Ritchey-Chrétien astrograph has:
• 8" f/8 true Ritchey-Chrétien hyperbolic mirror optical design
• low thermal expansion quartz primary and secondary mirrors, not ordinary optical glass
• 99% reflectivity non-tarnishing dielectric mirror coatings, not lower reflectivity aluminum coatings
• high strength/low thermal expansion carbon fiber optical tube, not merely rolled steel
• ten contrast-enhancing main tube light baffles, not eight
• dual-speed Crayford focuser
• 2" and 1.25" compression ring eyepiece holders
• two dovetail rails – one Vixen-style and one Losmandy-style “D-plate" – not simply a single Vixen-style dovetail
• an optional reducer/field flattener is available
Features of this Astro-Tech AT8RC Astrograph . . .
Optical design: true Ritchey-Chrétien Cassegrain-type two-mirror optics, with hyperbolic primary and secondary mirrors.
Aperture: 8", 1625mm focal length, f/8 focal ratio.
Hyperboloid primary mirror: Made of low thermal expansion quartz, rather than simple optical glass. Ground and polished under precision computer control. 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 AT8RC primary mirror is fixed to eliminate image shift and focus changes.
Hyperboloid secondary mirror: Made of low thermal expansion quartz, rather than simple optical glass. Ground and polished under precision computer control. 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 AT8RC secondary mirror is fixed and focusing is done externally.
99% reflectivity dielectric coated optics: Both primary and secondary mirrors have non-tarnishing state-of-the-art dielectric mirror coatings. These have a full 99% reflectivity for the brightest possible images. This is substantially higher than the 88% reflectivity of conventional aluminum coatings or the 94-96% reflectivity of enhanced aluminum coatings.
Carbon fiber optical tube: Made of light weight/high strength woven carbon fiber-reinforced composite material with extremely low thermal expansion characteristics to reduce the possibility of temperature-related focus changes that can occur with lesser steel tube systems. Die-cast and machined aluminum front and rear cells. The 9" o.d. x 18" long carbon fiber tube is virtually indestructible. The use of a carbon fiber composite reduces the weight of the optical tube with no loss of strength or rigidity compared to an aluminum tube. Because of the use of a carbon fiber optical tube, the weight of this 8" R-C is only a little more than two pounds heavier than the steel tube 6" Astro-Tech R-C.
Multiple internal light baffles: Computer optimized primary and secondary baffling. Ten contrast-enhancing glare-stop baffles in the optical tube, rather than eight; 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.
Dual-speed Crayford focuser: A 2" Crayford focuser is threaded onto the 90mm x 1mm pitch rear cell of the AT8RC. 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.
The weight of very heavy equipment trains (camera, plus filter wheel, plus temperature-compensated electric focuser, etc.) may cause the focuser drawtube to tilt slightly when fully extended, affecting the focus. Two threaded extension tubes are provided to install singly or in combination between the AT8RC rear cell and the focuser. These provide a flex-free solid metal extension that changes the distance between the focuser and the rear cell. This lets you accommodate the varying back-focus requirements of visual observing with eyepiece and diagonal versus DSLR-type camera imaging versus CCD imaging, while minimizing the need to extend the focuser drawtube. Additional optional threaded extension tubes are available to fine-tune the back focus as needed, as well as optional Astro-Tech 2" compression ring extension tubes that fit into the focuser drawtube.
For exceptionally long and heavy imaging equipment trains, the standard Crayford focuser can be user-replaced by an optional Feather Touch focuser from Starlight Instruments. This requires a 90mm x 1mm pitch rear cell thread to Feather Touch adapter available directly from Starlight Instruments.
Two 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" accessory holder on the drawtube, the 1.25" adapter also uses a non-marring soft brass compression ring.
Two dovetail mounting rails: Two dovetail rails are provided for installing the AT8RC on an equatorial mount, as well as for mounting optional accessories (such as a photoguide scope) on top of the AT8RC. One is a Losmandy-style “D-plate" dovetail rail that runs the full length of the underside of the optical tube, for installing the AT8RC on a Losmandy-style equatorial mount. The second is a Vixen-style dovetail rail that runs the full length of the top of the tube. This can be used for installing a photoguide ring set, piggyback camera adapter, or any other accessory that attaches to a scope by means of Vixen-style dovetail adapters. If the AT8RC is rotated 180°, it will bring the Vixen-style rail to the bottom of the tube so it can be used to install the AT8RC on a Vixen-style equatorial mount. Providing two dovetail rails on the Astro-Tech AT8RC does not limit your choice of mounts or accessory mounting options, as can happen with similar scopes provided with only one mounting rail.
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 AT8RC is protected by a two-year limited warranty against flaws in materials and workmanship.
Fully multicoated quartz and BK7 mirrors: The primary mirror of the 6” Astro-Tech is first-quality BK7 optical glass, while the 8” and larger Astro-Tech RCs use primary mirrors of low thermal expansion quartz for maximum focus stability during long exposure imaging sessions. Both 6” R-C mirrors are vacuum-coated with enhanced aluminum for high reflectivity and overcoated with a durable layer of silicon monoxide (quartz) for long life. The 8” and larger mirrors are dielectric coated for long life and reflectivity approaching 99%+.
Computer designed and fabricated optics: To keep the cost of each Astro-Tech RC so reasonable when compared to competitive RC scopes, the computer-optimized Astro-Tech hyperboloid mirrors are automatically ground and finished to very high tolerances using custom-made computerized mirror grinding machines. This precision computer control guarantees an exact repeatability of figure from mirror to mirror that is difficult to achieve using more costly conventional hand figuring. After grinding and polishing, each mirror is individually tested using a Zygo interferometer to assure that it meets or exceeds its specified surface accuracy.
Frill-free design: To further keep its cost reasonable, an Astro-Tech RC does away with most of the bells and whistles found on competitive scopes that add little to their performance (but much to their cost). For example, Astro-Tech front and rear cells are first die-cast, then CNC machine-finished, rather than completely CNC machined from raw stock at considerably greater expense but no significant improvement in performance as is the case with other RCs. Glare stops in the optical tube are a molded insert, rather than machined aluminum, resulting in a significant savings in cost at no appreciable difference in performance. The Astro-Tech scopes use an external manual dual-speed Crayford focuser, rather than the considerably more complicated and much more costly motorized movable secondary mirror system that other manufacturers use for focusing. The result of the Astro-Tech no-frills approach is genuine Ritchey-Chrétien wide-field performance at a fraction the cost of other commercial RC systems. While the mechanical bells and whistles may be limited in an Astro-Tech RC, an Astro-Tech scope still has the high precision flat field/coma-free true Ritchey-Chrétien optics that are the most important reason for buying an RC scope.