Ritchey-Chrétien telescope with a diameter of 304mm (12") and focal length of 2432mm, focal ratio f/8.
Ritchey-Chrétien (RC) telescopes are known for their fantastic optical performance, especially when focusing on photographic applications. But at the same time, Ritchey-Chrétien scopes have also been notorious for their really high prices. To try to change this dynamic, the popular manufacturer GSO (Guan Sheng Optical), widely known for its excellent Newton tubes, started making Ritchey-Chrétien telescopes.
The result of this decision has been the production of an instrument that is superior in many respects to the conventional Schmidt-Cassegrain and at a price that can still be considered affordable.
Advantages of having a Carbon Fiber tube:
- Greater lightness (only 18Kgs in a 12" tube)
- Virtually no change in tube length with temperature changes, therefore the focus is not affected by thermal contraction issues
The GSO Ritchey-Chrétien 12" f/8 Astrograph was designed to offer a 60mm illuminated field (including the optional RC corrector). Without the corrector, the illuminated field becomes 30mm.
Since the Ritchey-Chrétien optical system does not require corrector lenses or plates, a clean image without false colors or chromatic aberrations is obtained.The use of IR CUT (Infrared blocking) filters is also unnecessary, thus helping to increase the amount of light captured by the instrument.
Technical Specifications:
Optical Design: authentic Ritchey-Chrétien with hyperbolic primary and hyperbolic secondary mirror. Does not incorporate corrective plates or lenses in the optical train.
Optical Characteristics: 12" (304mm) diameter, 2432mm focal length and f/8 focal ratio.
Primary Mirror: Quartz surface and 1/12 wavelength quality or better. The primary has a high reflectivity dielectric optical treatment offering a reflection coefficient of 99%.
Secondary Mirror: Quartz. The secondary mirror has a high reflectivity dielectric optical treatment offering a 99% reflection coefficient . Integrated in a robust collimatable cell. The central obstruction is 112mm (44%).
Tube: carbon fiber tube with metallic cells to support the primary and secondary. Complete weight of 18 Kg. Tube length of 960mm including 3" focuser. Tube diameter 356mm.
Computer-optimized Baffle System: The inside of the tube has a series of PC-designed Baffles (undulations or partial barriers) designed to optimize the suppression of internal reflections or residual light.
Backfocus: 110mm from the 2" connection (sufficient for attaching CCDs with accessories).
Focuser: 3" Monorail focuser with high loading capacity (see NOTE BELOW).
Dovetail: The tube has a Losmandy type dovetail on the bottom (3" thick) which makes it compatible with Losmandy and CELESTRON CGEM, CGEM DX and CGE PRO mounts.
The 3" Monorail focuser is much more than a simple Crayford
The 3" Monorail focuser goes much further than a Crayford focuser does. The load is not only supported by 4 ball bearings, which in most cases are undersized, but by a stainless steel guide located in the base, thus preventing flexing even when working with heavy weights.
what is delivered with the telescope?
* RC 12" F/8 astrograph
* Monorail Crayford 3" focuser with 2" and 1.25" adaptor
* Dovetail type Losmandy (3")
Technical details:
Focusing travel: 80mm
Free aperture: 68mm
Precision focuser with double speed ratio 1:10
360º rotation
Adaptor to 2" and female thread M69
OPTICAL ADVANTAGES OF RITCHEY-CHRÉTIEN ASTRÓGRAFOS FROM GSO
Optical design: True Ritchey-Chrétien (True RC)
The GSO Ritchey-Chrétien astrographs are true, pure reflecting telescopes. Unlike the Maksutov or Schmidt-Cassegrain systems that have spherical mirrors and therefore need correctors, or the pure newtons that always need a coma corrector, the Ritchey-Chrétien systems are very well corrected by themselves without the use of corrector lenses and this makes them an ideal instrument for astrophotography.
RCs have a concave hyperbolic primary mirror and a convex hyperbolic secondary mirror.
The resulting image is fully corrected over the entire field while achieving an image sharpness on the optical axis far superior to that achieved with a traditional Schmidt-Cassegrain or Newton.
It is for this reason that Ritchey-Chrétien telescopes are very popular for astrophotography. The Ritchey-Chrétien configuration is the most frequently used design for professional telescopes such as the 10-meter Keck telescope in Hawaii or the VLT in Chile. Therefore, GSO puts a Ritchey-Chrétien optical design at the service of amateurs but without needing NASA's budget!!!!
99% high reflectivity Dielectric Coating
The primary mirror of the GSO Ritchey-Chrétien 8" telescope is made of Quartz, which like Zerodur, has a near zero thermal expansion coefficient, allowing it to provide excellent optical performance as the temperature drops as the night progresses. Both the primary and secondary mirrors have a 99% reflection coefficient and are treated to protect the mirror from scratching and aging. Compared to similar instruments, more effective light collection is achieved.
Each optical kit is verified by the manufacturer
To maintain the optical quality level, each optical kit is checked and corrected by hand after leaving the automated production process. The optical kit is then verified with a Zygo interferometer.
