GSO 4.5" f/12 Classical Cassegrain Carbon Fiber Reflector Telescope
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- Classical cassegrain telescope with 4.5” aperture and focal ratio of f/12, ideal for visual observation and imaging of the Moon, planets, double stars, planetary nebulae, and other compact celestial objects
- Fully and rigorously tested on site for cosmetics, mechanical operation, and optical performance by a master optician to ensure excellent overall telescope operation and customer satisfaction (an Agena exclusive service)
- Folded optical design packs a focal length of 1368mm into an optical tube only 409mm / 13.1" long, making it an ideal travel companion
- No glass corrector plate means no chromatic aberration and fast temperature equalization and resistance to dew formation
- Lightweight tube and optics for a total weight of 4lbs-13oz, ideally matched to many mid-capacity alt-az and equatorial mounts
- EAF-compatible dual-speed 2” Crayford focuser with M56x0.75 thread and 1.25” adapters with non-marring compression rings
- Includes Vixen-style dovetail rail, 1" long M90-threaded spacer rings (2x), shoe for finder scope, and dust caps
1. A Modern Take on a Classic Telescope Design
First conceived in 1672, the classical Cassegrain telescope uses a parabolic primary mirror and a hyperbolic secondary mirror to fold a long focal length into a relatively compact open optical tube. This simple design is ideal for visual observations of the Moon, planets, double stars, planetary nebulae, compact globular clusters, and other objects that are well framed in the tighter fields of view that result from a long focal length.
This 4.5" f/12 Cassegrain from GSO is a modern take on the classical Cassegrain design. With a focal length of 1368mm, it's ideal for crisp and razor-sharp visual observation and imaging. This telescope offers views that rival apochromatic refractors at a fraction of the price. Despite its long focal length, the optical tube of this telescope is just 305mm / 12in long excluding the focuser and 409mm / 16.1in long including the focuser and front dust cover.
Compared to more complex Maksutov-Cassegrain designs, which include a thick and heavy corrector plate, this scope is not only far less expensive, it's also much lighter at just over 4.5 lbs, which matches well with nearly any mid-capacity altazimuth or equatorial mount. Unlike compound telescopes like Maksutov or Schmidt-Cassegrains, these telescopes have fixed mirrors so there's no image shift or mirror flop during focusing, even at very high magnifications. And since they are purely reflecting telescopes, there is no chromatic aberration visible, even when observing bright objects.
2. Full Optical and Mechanical Testing and Quality Control - An Agena Exclusive!
GSO telescopes are available from several suppliers, but Agena does much more than simply move the telescope boxes from GSO to you. Each GSO Cassegrain telescope at Agena undergoes a thorough physical, mechanical, and optical evaluation at our shop upon arrival - all at no extra cost to you.
Every GSO telescope is inspected to ensure good cosmetics, collimation, smooth focuser operation, and to make sure all parts are included by the manufacturer. Most importantly, we also check each telescope using a rigorous three-point on-site optical evaluation consisting of the following optical bench tests to ensure that your telescope delivers excellent optical performance:
- Foucault Test: This knife-edge test is performed at the center of curvature of the primary mirror to evaluate the quality of the mirror's conic shape.
- Ronchi Test: We then perform a Ronchi grating test at the center of curvature at inside focus, at focus, and outside focus. This is a qualitative method to evaluate primary mirror smoothness and figure.
- Star test: Finally, we collimate the complete telescope and perform an autocollimation test with an artificial star to examine the overall system's image performance at the focus point.
This testing is performed and certified by a master optician to make sure each GSO instrument sold by Agena has excellent optical performance before it ships. Each telescope should be ready to go out of the box when you receive it.
3. Diffraction Limited BK-7 Mirrors for Razor-Sharp Views
Both the parabolic primary and hyperbolic secondary mirrors are made from BK-7 optical glass and ground and polished to a surface accuracy that is diffraction limited or better. Each mirror has enhanced aluminum coatings overcoated with a protective layer of quartz for long life. And each has a reflectivity of better than 96%, similar to Ritchey-Chretien, Schmidt-Cassegrain, and other scopes that cost far more. The secondary mirror is mounted in a four-vane spider, and the central obstruction is about 19% (by area).
These telescopes are ideal for visual observation, but they can also be used for lunar and planetary imaging. While these telescopes do not exhibit spherical aberration, like Newtonians they will have some coma especially at the lowest magnifications or with astronomy cameras with large chips.
4. EAF-Compatible 2" Dual-Speed Crayford Focuser and Accessories
The telescope comes with a 2" dual-speed Crayford focuser mounted to the M90x1 threads on the rear cell. There's a coarse focusing knob on each side and a single 10:1 fine focusing knob on one. The drawtube includes a non-marring soft brass compression ring to hold 2" accessories in place. An included 1.25" adapter, also with a non-marring compression ring, slips into the 2" focuser to hold 1.25" eyepieces or imaging accessories. Users seeking to replace this focuser to eliminate the slight focuser slop present in most Crayford focusers or have a heavier load lifting capacity can consider GSO's linear bearing focusers to replace the stock focuser with (sold separately).
The focuser is compatible with ZWO's EAF out of the box (no additional adapters are required).
The focuser drawtube has 38mm of travel and terminates in an M56x0.75 male thread (before the 1.25" eyepiece adapter). This allows the use of accessories such as Baader's clicklock visual back (# 2956255) or other M56-threaded adapters for direct connection to cameras and other accessories should you wish to do so.
This telescope has a generous available back focus of 150mm (from the 1.25" eyepiece adapter and with the focuser fully racked in) for most imaging applications. Also included are two 1" long M90-threaded extension tubes. You can insert these between the OTA and the focuser should you need to reduce the available back focus for imaging applications.
5. Open Aluminium and Carbon Fiber Tube for Fast Temperature Equalization, Reduced Dew Formation and Reduced Weight
The black tube of this classical Cassegrain is made from carbon fiber for good thermal stability and low weight. It is capped with aluminium end rings for protection and rigidity. The scope includes a dust cap, a Vixen-style shoe for a finder scope, and a Vixen-style dovetail rail for mounting.
Because there is no corrector plate on this classical Cassegrain design, the optics are far less susceptible to dewing, and they exhibit much faster temperature equalization because of the open optical tube. The absence of a corrector plate also means this telescope is ideal for imaging planets in the IR to pick up additional detail not seen at visible wavelengths.
6. Specifications
- Optical design: Classical cassegrain reflector
- Aperture: 114mm (4.5")
- Focal ratio: f/12
- Focal length: 1368mm
- Primary mirror: Parabolic primary mirror; minimum 96% reflectivity; protective quartz layer
- Secondary mirror: Hyperbolic secondary mirror; minimum 96% reflectivity; protective quartz layer; center dot marked for collimation
- Secondary mirror holder: 4-vane all metal spider; 3 collimation screws (M4x0.75) for alignment of secondary mirror
- Secondary mirror diameter: 48.5mm
- Secondary obstruction (by diameter): 43.9%
- Secondary obstruction (by area): 19.2%
- Available back focus (distance of focal plane from surface of 2" eyepiece adapter, with focuser full racked in): 150mm
- Tube outside diameter: 131mm
- Tube length: 12" (305mm)
- Tube material: Aluminium and carbon fiber
- Extension tubes: 94mm(3.7" OD) x 1" - 2x
- Focuser: 2" EAF-compatible dual-speed Crayford
- Tube weight (with all included accessories): 4lbs-13oz
- Inspected for collimation and focuser operation at Agena AstroProducts
- Warranty: 2 years
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free Contiguous US Shipping |
| Telescope Focal Length | 1251 - 1500mm |
| Hide Found a better Shipped Price on Frontend? | Yes |
- Classical cassegrain telescope with 4.5” aperture and focal ratio of f/12, ideal for visual observation and imaging of the Moon, planets, double stars, planetary nebulae, and other compact celestial objects
- Fully and rigorously tested on site for cosmetics, mechanical operation, and optical performance by a master optician to ensure excellent overall telescope operation and customer satisfaction (an Agena exclusive service)
- Folded optical design packs a focal length of 1368mm into an optical tube only 409mm / 13.1" long, making it an ideal travel companion
- No glass corrector plate means no chromatic aberration and fast temperature equalization and resistance to dew formation
- Lightweight tube and optics for a total weight of 4lbs-13oz, ideally matched to many mid-capacity alt-az and equatorial mounts
- EAF-compatible dual-speed 2” Crayford focuser with M56x0.75 thread and 1.25” adapters with non-marring compression rings
- Includes Vixen-style dovetail rail, 1" long M90-threaded spacer rings (2x), shoe for finder scope, and dust caps
1. A Modern Take on a Classic Telescope Design
First conceived in 1672, the classical Cassegrain telescope uses a parabolic primary mirror and a hyperbolic secondary mirror to fold a long focal length into a relatively compact open optical tube. This simple design is ideal for visual observations of the Moon, planets, double stars, planetary nebulae, compact globular clusters, and other objects that are well framed in the tighter fields of view that result from a long focal length.
This 4.5" f/12 Cassegrain from GSO is a modern take on the classical Cassegrain design. With a focal length of 1368mm, it's ideal for crisp and razor-sharp visual observation and imaging. This telescope offers views that rival apochromatic refractors at a fraction of the price. Despite its long focal length, the optical tube of this telescope is just 305mm / 12in long excluding the focuser and 409mm / 16.1in long including the focuser and front dust cover.
Compared to more complex Maksutov-Cassegrain designs, which include a thick and heavy corrector plate, this scope is not only far less expensive, it's also much lighter at just over 4.5 lbs, which matches well with nearly any mid-capacity altazimuth or equatorial mount. Unlike compound telescopes like Maksutov or Schmidt-Cassegrains, these telescopes have fixed mirrors so there's no image shift or mirror flop during focusing, even at very high magnifications. And since they are purely reflecting telescopes, there is no chromatic aberration visible, even when observing bright objects.
2. Full Optical and Mechanical Testing and Quality Control - An Agena Exclusive!
GSO telescopes are available from several suppliers, but Agena does much more than simply move the telescope boxes from GSO to you. Each GSO Cassegrain telescope at Agena undergoes a thorough physical, mechanical, and optical evaluation at our shop upon arrival - all at no extra cost to you.
Every GSO telescope is inspected to ensure good cosmetics, collimation, smooth focuser operation, and to make sure all parts are included by the manufacturer. Most importantly, we also check each telescope using a rigorous three-point on-site optical evaluation consisting of the following optical bench tests to ensure that your telescope delivers excellent optical performance:
- Foucault Test: This knife-edge test is performed at the center of curvature of the primary mirror to evaluate the quality of the mirror's conic shape.
- Ronchi Test: We then perform a Ronchi grating test at the center of curvature at inside focus, at focus, and outside focus. This is a qualitative method to evaluate primary mirror smoothness and figure.
- Star test: Finally, we collimate the complete telescope and perform an autocollimation test with an artificial star to examine the overall system's image performance at the focus point.
This testing is performed and certified by a master optician to make sure each GSO instrument sold by Agena has excellent optical performance before it ships. Each telescope should be ready to go out of the box when you receive it.
3. Diffraction Limited BK-7 Mirrors for Razor-Sharp Views
Both the parabolic primary and hyperbolic secondary mirrors are made from BK-7 optical glass and ground and polished to a surface accuracy that is diffraction limited or better. Each mirror has enhanced aluminum coatings overcoated with a protective layer of quartz for long life. And each has a reflectivity of better than 96%, similar to Ritchey-Chretien, Schmidt-Cassegrain, and other scopes that cost far more. The secondary mirror is mounted in a four-vane spider, and the central obstruction is about 19% (by area).
These telescopes are ideal for visual observation, but they can also be used for lunar and planetary imaging. While these telescopes do not exhibit spherical aberration, like Newtonians they will have some coma especially at the lowest magnifications or with astronomy cameras with large chips.
4. EAF-Compatible 2" Dual-Speed Crayford Focuser and Accessories
The telescope comes with a 2" dual-speed Crayford focuser mounted to the M90x1 threads on the rear cell. There's a coarse focusing knob on each side and a single 10:1 fine focusing knob on one. The drawtube includes a non-marring soft brass compression ring to hold 2" accessories in place. An included 1.25" adapter, also with a non-marring compression ring, slips into the 2" focuser to hold 1.25" eyepieces or imaging accessories. Users seeking to replace this focuser to eliminate the slight focuser slop present in most Crayford focusers or have a heavier load lifting capacity can consider GSO's linear bearing focusers to replace the stock focuser with (sold separately).
The focuser is compatible with ZWO's EAF out of the box (no additional adapters are required).
The focuser drawtube has 38mm of travel and terminates in an M56x0.75 male thread (before the 1.25" eyepiece adapter). This allows the use of accessories such as Baader's clicklock visual back (# 2956255) or other M56-threaded adapters for direct connection to cameras and other accessories should you wish to do so.
This telescope has a generous available back focus of 150mm (from the 1.25" eyepiece adapter and with the focuser fully racked in) for most imaging applications. Also included are two 1" long M90-threaded extension tubes. You can insert these between the OTA and the focuser should you need to reduce the available back focus for imaging applications.
5. Open Aluminium and Carbon Fiber Tube for Fast Temperature Equalization, Reduced Dew Formation and Reduced Weight
The black tube of this classical Cassegrain is made from carbon fiber for good thermal stability and low weight. It is capped with aluminium end rings for protection and rigidity. The scope includes a dust cap, a Vixen-style shoe for a finder scope, and a Vixen-style dovetail rail for mounting.
Because there is no corrector plate on this classical Cassegrain design, the optics are far less susceptible to dewing, and they exhibit much faster temperature equalization because of the open optical tube. The absence of a corrector plate also means this telescope is ideal for imaging planets in the IR to pick up additional detail not seen at visible wavelengths.
6. Specifications
- Optical design: Classical cassegrain reflector
- Aperture: 114mm (4.5")
- Focal ratio: f/12
- Focal length: 1368mm
- Primary mirror: Parabolic primary mirror; minimum 96% reflectivity; protective quartz layer
- Secondary mirror: Hyperbolic secondary mirror; minimum 96% reflectivity; protective quartz layer; center dot marked for collimation
- Secondary mirror holder: 4-vane all metal spider; 3 collimation screws (M4x0.75) for alignment of secondary mirror
- Secondary mirror diameter: 48.5mm
- Secondary obstruction (by diameter): 43.9%
- Secondary obstruction (by area): 19.2%
- Available back focus (distance of focal plane from surface of 2" eyepiece adapter, with focuser full racked in): 150mm
- Tube outside diameter: 131mm
- Tube length: 12" (305mm)
- Tube material: Aluminium and carbon fiber
- Extension tubes: 94mm(3.7" OD) x 1" - 2x
- Focuser: 2" EAF-compatible dual-speed Crayford
- Tube weight (with all included accessories): 4lbs-13oz
- Inspected for collimation and focuser operation at Agena AstroProducts
- Warranty: 2 years
| Product Banner Type | new |
|---|---|
| Free Shipping Graphic | Free Contiguous US Shipping |
| Telescope Focal Length | 1251 - 1500mm |
| Hide Found a better Shipped Price on Frontend? | Yes |
GSO 4.5" f/12 Classical Cassegrain Carbon Fiber Reflector Telescope # CC45-C