Astrograph tube TS Ritchey-Chrétien 8 Metal

Ritchey-Chrétien telescope with a diameter of 203mm and focal length of 1624mm, 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 manufacturing 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.

The Astrograph GSO Ritchey-Chrétien 8" f/8 was designed to offer an illuminated field on the 35mm format (24x36mm). For cameras with a smaller sensor, which are basically most CCD cameras, the use of a field flattener is not even necessary. For cameras with larger CCD's the use of a field flattener is recommended.

Since the Ritchey-Chrétien optical system does not require corrective lenses or plates, a clean image without false colors or chromatic aberrations is obtained. IR CUT (Infrared blocking) filters will also not be necessary, helping to increase the amount of light captured by the instrument

how to bring a DSLR camera into focus?

The GSO Ritchey-Chrétien telescope has a generous backfocus, allowing the attachment of multiple accessories such as off-axis radial guides, filter wheels, etc. If you want to take pictures with a DSLR camera working at prime focus or without intermediate accessories and without the focuser being in a very extreme position, it will be necessary to attach some spacer accessories:

- GSRCV50: 50mm spacer to be placed between the focuser and the telescope.

- TSFA240: T-adapter with 40mm extension.

Technical Specifications:

Optical Design: authentic Ritchey-Chrétien with hyperbolic primary and hyperbolic secondary mirror. No correction plates or lenses in the optical train.

Optical Characteristics: 8" (203mm) diameter, 1624mm 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. Obscuration is 42.5%.

Tube: metal tube with metal cells to support the primary and secondary. Complete weight of 7.5 Kg.

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.

Focuser: Crayford 1:10 focuser for extremely smooth focusing. The 1:10 dual speed focuser (dual speed focuser) is basic for good performance in astrophotography. There will be no image movement (shift that is usually caused by the primary mirror) and it has a load capacity of up to 5kg! The focuser accepts 2" and 1.25" accessories.

Dovetail: The tube has a dovetail type Vixen (narrow for GP type mounts) at the bottom. Therefore it can go with any mount that has a Vixen GP type head.

The 2" Monorail focuser is much more than a simple Crayford

what comes with the telescope?

* RC 8" F/8 astrograph
* 2" Crayford focuser with 1.25" adapter
* 2x dovetails type Vixen, one at each end of the tube

Technical details:

Weight: 7.5 kg
Obstruction: 97 mm
Tube length: 580 mm including focuser
Tube diameter: 230 mm
Dovetail length: 395 mm
Extender tube needed for 2" zenith mirror: 50mm
Extender tube needed for 1.25" zenith mirror: 80mm

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.