The Cassegrain telescope - considered extinct, but again comes back to the game thanks to the Taiwanese GSO factory. We hope that it will return permanently, because this construction offers a lot of unique features and we are sure that it is very worth paying attention to it.
• cools faster than Schmidt-Cassegrain and Maksutow-Cassegrain (similar to RC Newtons)
• there is not even a residual chromatic aberration, because it is a telescope that works only on reflection, not light deflection (like RC and Newton telescopes)
• has a longer focal length than a typical RC or Newtonian one, and parametrically similar to the Maksutov telescope
• very compact design (similar to RC and Mak)
• no lens system allows the use of the Cassegrain telescope in infrared photography
• the long focal length facilitates the collimation procedure, which is a shortcoming of RC telescopes, especially if you plan to use them as an exit telescope.
In general, the Cassegrain system is - as you can read - the main mirror with the figure of a rotational and secondary paraboloids being a segment of a rotational hyperboloid. A typical drawback of these is the difficulty in making these surfaces - but this is what the GSO factory dealt with. Others include a long focal length and therefore not a large field of view - but this is often an advantage, as it eliminates flaws on the edges of the field, and at the same time gives a high scale of reproduction both in photography and in observations.
Purpose : visual observations, planetary astrophotography, compact astrophotography with high-sensitivity cameras, infrared photography.
• construction: the classic Cassegrain telescope
• active diameter: 8 "/ 203 mm
• focal length: 2436 mm
• lighted up: f / 12
• resolving power: 0.59 "
• star range for visual observations: 13.6 mag
• glass: quartz in the primary and secondary mirror
• reflectance: 99% for each of the mirrors
• obstruction (linear, relative to diameter): 33%
• extractor: 2 "with 1.25" reduction, with a 10: 1 microfocus box
• two extension extensions on the M90 thread (50 mm optical length each) included
• back focus: 150 mm from the end of the 2 "lift
• tube diameter: 230 mm
• finder foot: yes, in Vixen standard
• dovetail: yes, in the Vixen standard
• length: approx. 620 mm
• weight: 7.5 kg
Below: test pictures on the Moon; setup: main telescope: GSO Cassegrain 8", camera: ZWO ASI 178 MM, filter: Baader Planetarium Solar Continuum (sic!); mount: EQ6-R
/ pics taken in Jan 2021; click to enlarge /
Below: Saturn and Jupiter pictures sent us from our customer in Italy; setup: ZWO ASI224mc + Celestron Luminos Barlow 2,5x; author: Mr. Alessandro Vinci
/ taken in late summer 2021; placed here with author's permission - thank you, Sir! /