GSO 8" RC

I purchased this scope as a replacement for the Celestron NexStar 8SE. It has the same aperture, but a different optical and mechanical design. Overall it is far more suited to astrophotography, whereas the NexStar is really designed for visual use.

The Ritchey Chrétien design is based around a hyperbolic primary and a secondary mirror. Like all telescopes, it's a compromise. In my view, the key benefits are as follows:

• Reduced coma
• Fixed Primary Mirror (does not move during imaging)
• Short tube length (performs better in windy conditions and easier to handle)
• No chromatic aberration (mirror only design)
• Open Tube design / No corrector plate (fast cool down and less dew build up than SCT or Mak-newt)
• Ideal camera location (easy to balance, fixed to back plate and primary / less tube sag)

Disadvantages:

• Field curvature
• Diffraction spikes
• No rear cooling fans on the 8" version
• Requires careful collimation

It is a relatively new product, manufactured by Guan Sheng Optical in Taiwan. The focuser is based around a Hiwin Linear Guideway. So far I have no issues with the focuser.

Specifications:

• Type : Ritchey-Chrétien
• Aperture : 203mm
• Focal Length : 1,625mm
• F number : f/8
• Acquired : September 2009
• Focuser travel : 50mm
• Guideway width : 9.00 mm

Guides

I have moved my guide to collimation here.

I have also developed a disassembly guide here.