GSO 8" F/12 M-LRS Classical Cassegrain Metal OTA (Black)

The Cassegrain telescope, once considered extinct, has made a comeback in the astronomical community, thanks to the efforts of the Taiwanese GSO factory. This revival is expected to be permanent, as the Cassegrain design offers numerous unique features that make it worthy of attention.

One of the notable advantages of the Cassegrain telescope is its rapid cooling capability, surpassing both the Schmidt-Cassegrain and Maksutov-Cassegrain designs. Similar to RC Newtonian telescopes, the Cassegrain operates solely on reflection, eliminating residual chromatic aberration caused by light deflection.

Furthermore, the Cassegrain telescope boasts a longer focal length compared to typical RC or Newtonian telescopes, making it similar in this regard to the Maksutov design. Despite its extended focal length, the Cassegrain maintains a compact design akin to RC and Mak telescopes.

A distinguishing characteristic of the Cassegrain system is its absence of a lens system, enabling the use of this telescope for infrared photography. Additionally, the long focal length simplifies the collimation procedure, addressing a common challenge faced by RC telescopes, particularly when used as an exit telescope.

In essence, the Cassegrain system comprises a main mirror with the shape of a rotational hyperboloid segment, complemented by a secondary paraboloid mirror. While the production of these surfaces presents difficulties, the GSO factory has successfully overcome these challenges. Other drawbacks associated with Cassegrain telescopes, such as the longer focal length and narrower field of view, often prove advantageous by eliminating distortions at the field edges and delivering high-scale reproduction in photography and observations.

The Cassegrain telescope finds utility in various applications, including visual observations, planetary astrophotography, compact astrophotography with high-sensitivity cameras, and infrared photography.

Technical Specifications:

• Design: Classic Cassegrain telescope
• Aperture: 8" / 203 mm
• Focal Length: 2436 mm
• Focal Ratio: f/12
• Resolving Power: 0.59"
• Visual Observing Limit: 13.6 magnitude
• Primary and Secondary Mirror Material: Quartz
• Mirror Reflectivity: 99% for each mirror
• Obstruction (linear, relative to diameter): 33%
• Focuser: 2" with 1.25" reduction and a 10:1 microfocus knob
• Includes two extension tubes (50 mm optical length each) with M90 threading
• Back Focus: 150 mm from the end of the 2" focuser drawtube
• Tube Diameter: 230 mm
• Finder Scope Mount: Vixen standard
• Dovetail: Vixen standard
• Length: Approximately 620 mm
• Weight: 7.5 kg
• Warranty: 24 months