TS GSO 6" f/9 RC Ritchey-Chrétien Telescope.

Most large professional telescope are designed and constructed to the Ritchey-Chrétien principle. Until recently, these telescopes were unaffordable for amateurs as they are quite difficult and complex to produce, due to their unique design, Ritchey-Chrétien telescopes are primarily aimed to amateur astronomers with an interest in high resolution Astrophotography however an RC can also still be used for visual observing with an eyepiece if needed.

How to reach focus on the 6" RC:
Without extension sleeves, the back focus from the 2" connection is about 159mm. But included are three M90 extension sleeves (1x 50mm 2x 25mm) which are simply screwed between the focuser and the tube. This allows you to focus any accessory needed such as 1.25" and 2" zenith mirrors and also various correctors and most common cameras.

Astrophotography with the TS 6" RC telescope:
Better and sharper astro photos without a corrector and with shorter exposure times is exactly what this Ritchey-Chrétien telescope allows you to do with astro cameras and SLRs up to APS-C sensors. As a pure mirror system, you can even use the infrared light. You can achieve up to 25% shorter exposure times and sharper imaging than, for example, through a comparable Schmidt-Cassegrain telescope. For the use of a reflex camera without focal length reduction you need the 50mm and the 25mm extension between focuser and telescope.

The generous backfocus also allows the connection of correctors (which we recommend for the use of full-frame sensors). You can also connect a focal length reducer, thus further increasing the light intensity of the Ritchey-Chrétien.

Accessories - 0.67x CCD reducer for Astrophotography:
The CCD47 reducer improves the focal ratio from f/9 to f/5.96, therefore reducing the exposure time by around 50%. With this, you can capture dim nebulae and galaxies with more moderate exposure times.

Primary and secondary mirror of quartz glass with 94% enhanced reflectivity:
Quartz glass does not change its dimensions if temperature changes. When the temperature changes slowly during an exposure, other mirror substrates, like Pyrex, tend to a deformation of the mirror and thus to a shift of the focus. This problem does not exist for mirrors of quartz glass. Therefore the focus is better maintained which is very important for long exposures. Both mirrors are coated with 94% reflectivity material which means the image is obviously brighter than many other designs with only 90% reflection.

The advantages of TS Ritchey-Chrétien telescopes for Astrophotography:
The TS RC astrographs are true Ritchey-Chrétien telescopes. Maksutovs and Schmidt-Cassegrains have spherical mirrors and need correctors for making a large field usable. With Schmidt-Cassegrains, you can see the aberrations in the field even when working visually. Most times, Maksutov-Cassegrains are so slow that they are not suitable for astrophotography. RC telescopes have hyperbolical primary and secondary mirrors. They are more difficult to manufacture, but offer a significantly sharper field with less aberrations throughout the field.

What makes the Ritchey-Chrétien Telescope superior to Schmidt-Cassegrain telescopes for Astrophotography:
Schmidt-Cassegrains generally require a corrector for Astrophotography. Additionally, these telescopes have a Schmidt plate at the front side which is prone to dew. The RC is a pure reflection system without lenses in the light path. Thus you can use the complete light even in the infrared range. The image is brighter and the exposure times get shorter. The field of an RC telescope is coma-free by design and relatively flat.

No shifting problem with TS RC telescopes:
Telescopes with focusing via a movable primary mirror often suffer from mirror shifting problems. The image shifts while focusing or even jumps. TS Ritchey-Chrétien telescopes do not have this problem, as their primary mirror is fixed. Focusing is done via a high-quality focuser. An additional advantage is the optimal distance from primary to secondary mirror which gives you the guarantee of the best possible image if the primary mirror moves relative to the secondary, you will almost never have the optimal distance.

Telescope Spec:

• Optical Design: True Ritchey-Chrétien with a hyperbolic primary and secondary mirror.
  
• Aperture: 6" / 154mm
  
• Focal Length: 1370mm (918mm using the CCD47 Reducer)
  
• Focal Ratio: f/9 (f/5.96 using the CCD47 reducer)
  
• Resolution: 0.76"
  
• Reflectivity: 94% reflectivity non-tarnishing mirror coatings
  
• Back Focus: 159mm from 2" connection of the focuser
  
• Tube Diameter: 191mm
  
• Tube Length: 500mm with focuser
  
• Tube Weight: 5.4kg
  
• Obstruction by secondary: 77mm
  
• Focuser: 2" dual speed Crayford focuser
  
• Connecting Thread: M90x1
  
• Dovetail Bar: 1x GP style

What's included:

1. 6" f/9 RC Astrograph
   
2. 2" Crayford focuser with 1.25" adaptor
   
3. Vixen style dovetail bar
   
4. M90 Extension rings 1x 50mm and 2x 25mm
   
5. Dust cover