Classical Cassegrain telescope
This 8” f/12 Classical Cassegrain telescope is a modern take on the classical Cassegrain design. With a focal length of 2436mm, it’s ideal for crisp and razor-sharp visual observation and imaging. This telescope offers views that rival apochromatic refractors at a tiny fraction of the price. Despite its long focal length, the optical tube of this telescope is just 21.1” (536mm) long, not including the focusers.
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, just 20bs, which matches well with nearly any mid-capacity altazimuth or equatorial mount. And unlike compound telescopes like Maksutov or Schmidt-Cassegrains, these telescopes have fixed mirrors so there’s no image shift 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.
- Classical Cassegrain telescope with 8” 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 2436mm into an optical tube only 535mm long
- 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 just 20lbs, ideally matched to many mid-capacity alt-az and equatorial mounts
- Dual-speed 2” Crayford focuser with 1.25” adapters with non-marring compression rings
- Includes Losmandy and Vixen-style dovetail rails, shoe for finder scope, and dust cap
Both the parabolic primary and hyperbolic secondary mirrors are made from thermally-stable quartz and ground and polished to a surface accuracy that’s 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 33%, comparable to most Schmidt-Cassegrain telescopes.
These classical cassegrain 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.
Internal Light Baffles for High Contrast
Computer optimization results in eight contrast-enhancing glare-stop baffles in the optical tube as well as multiple glare-stop micro baffles in the secondary mirror light shield. The scope also includes four baffles in the primary mirror baffle tube, resulting in excellent dark sky backgrounds and extremely good image contrast.
2” Dual-Speed Crayford Focuser and Accessories
The classical cassegrain 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. 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. The scope also comes with adapter rings to help achieve focus in a wide range of visual and imaging configurations.
Open Metal Tube for Fast Temperature Equalization and Reduced Dew Formation
The black tube of this classical Cassegrain telescope is made from rolled steel for good thermal stability and it’s capped with end rings of die-cut aluminum for protection and rigidity. The scope includes a dust cap, a shoe for a finder scope, and Losmandy and Vixen-style dovetail rails for mounting.
Because there’s 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.