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The GSO 12" f/8 Ritchey Chretien Astrograph is a dream telescope for astrophotography. The telescope is fitted with a stable Carbon Fiber Truss tube and a precise 3" dual speed Monorail focuser. The GSO 12" f/8 Ritchey-Chretien Truss Tube Astrograph is a true RC telescope and will give you spectacular photo results also with large format camera sensors. But also visual observing is a highlight with this powerful telescope. The telescope is transportable and will be carried from mounts of the Skywatcher EQ8 class and upwards.

This RC telescope has been optimised especially for astro photography. The OTA comes with carbon trusses having a thermal expansion of nearly 0. The weight of the OTA is 24 kg and it has a Losmandy-style dovetail rail on both sides.

The GSO 12" f/8 RC Astrograph illuminates a maximum field diameter of approx. 60 mm. Without any corrector, 35 mm is possible. In the latter configuration, you have a pure mirror system without any lenses. You don´t need an IR cut filter and you can use the full spectrum with a suitable CCD camera.


  • Aperture 12" / 304mm
  • Focal Length 2432mm
  • Focal Ratio f/8
  • Carbon truss tube with 2 Losmandy Level dovetail bars
  • 99% dielectric high-reflectivy coating on main- and secondary mirror
  • Big corrected flat field without need for additional correctors
  • 3" MONORAIL Focuser with better stability


Back focus

The GSO RC has a generous back focus allowing to attach many accessories like off-axis-guiders, filter wheels and much more. The distance from the 2" connection of the focuser to the focal plane is 127mm. To reach the perfect focus position, we suggest the GSRCV1172 and GSRCV1175 extension rings. The position of the rings is between focuser and tube backside. So you always have a good position of the draw tube.

The Carbon Fiber Truss Tube Design

Lightweight yet strong carbon fiber truss tubes have low thermal expansion characteristics. Shifts in focus due to temperature changes are minimized because of this design. The trusses are also designed to flex equally, keeping the optics in collimation regardless of the position of the telescope.

The 3" M-LRN Monorail Focuser:

The 3" Monorail focuser is a further development of the crayford design. The load is not carried by four (often underdimensioned) ball bearings but on a stainless steel track on the base, thus preventing tilting and bending even under high loads. It is countered by a big knurled screw that centers the inner tube exactly to the rail. The load is distributed evely across the rail´s surface.

Specifications of the focuser:

  • Travel: ca. 80mm
  • Free aperture: 68mm
  • Guidance: by massive and fixed steel rail
  • 1:10 transmission for precise focusing
  • 360° Rotation
  • Adaption to 2" and (when screwed off) female M68 thread, directly fitting to TS Optics 2.5" off-axis-guider


The hyperbolic primary and hyperbolic secondary are made from low expansion quartz, and finished with a scratch-resistant highly reflective 99% dielectric coating for great contrast. The primary mirror is fixed in place in a metal mirror cell, and the secondary resides in a metal housing that can be collimated. The secondary mirror has a center mark for easy and accurate collimation.

Cooling Fans

The RC telescope has three small cooling fans in the rear cell that help create an ambient temperature within your telescope for more stable viewing and less fluctuation in focus. The fans are powered by an external battery pack. This battery holder accepts 8-AA batteries (sold separately).

A Fixed Primary Eliminates Image Shift

Schmidt-Cassegrain,m EHD, ACF... & Mak-Cassegrain telescopes achieve focus by moving the primary mirror back and forth inside the optical tube assembly, and this movement can cause image shift. While manufacturers have done a pretty good job of minimizing image shift on their telescopes, a moveable mirror makes it almost impossible to eliminate it completely. The Ritchey-Chretien has a primary that is fixed in place, removing the possibility of image shift and also the job of collimating the primary.

Why the RC Telescope is better than Schmidt Cassegrain telescopes with correctors

Schmidth-Cassegrain telescopes need a lens corrector wich is integrated in the optical system, whilst Ritchey-Chretiens are true reflection systems without lens corrector and therefore with a really bright image. This is also the advantage of RC telescopes against Celestron Edge HD or Meade ACF telescopes.

The optical advantages of TS RC (Ritchey Chretien“) Astrographs for astrophotography

The GSO RC Astrograph is a real Ritchey-Chrétien reflector telescope. Contrary to Maksutovs or Schmidt-Cassegrains which have spherical mirrors and need image correctors, and contrary to Newtonians that need coma correctors, the RC system is a well corrected photographical instrument that uses only mirrors (no false colour!) and does not require any corrector with most commercially available cameras.

12" F/8 M-LRC Ritchey-Chrétien Truss Tube Telescope OTA

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