Ritchey-Chrétien (RC) telescopes are highly prized for their excellent optical performance, especially for astrophotography. At the same time however RCs were always very expensive. To change this the well-known US-based distributor “Astro-Tech” asked GSO to produce true RC telescopes. GSO is best known for their excellent Newtonian optics which they have built for many years now.
The result of this joint venture is an affordable RC that is superior in most aspects to a conventional Schmidt-Cassegrain. Bintel is an Australian distributor for these instruments from GSO.
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6″ f/9 RC Astrograph
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2″ Crayford focuser with 1.25″ adaptor
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Vixen style dovetail plate
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Dovetail for finderscope
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Aperture (mm): 152
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Focal length (mm): 1370
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f/ ratio: 9
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Resolving capacity: 0.76′
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Limiting visual magnitude: 12.7
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Max. useful magnification: 304x
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Secondary mirror diameter (mm): 76
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Secondary mirror obstruction: 50%
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Weight: 5.8kg
The 6″ f/9 Astrograph is unique in offering ample aperture and long enough focal length to provide good image scale. Ideal for smaller deep sky targets such as galaxies, small globular clusters and planetary nebulae. Add to this its small overall dimensions and suberb image quality and you can begin to understand why it is an excellent option for portable astro-imaging applications.
The RC design uses no lenses or corrector plates so there is no false colour at all. It is also less prone to dew problems associated with corrector plates on Schmidt and Maksutov Cassegrain systems.
Optics (primary and secondary mirrors) use BK7 glass and feature 99% reflective dielectric coatings. These advanced coatings provide much higher light transmission compared to aluminium coatings on competing Schmidt Cassegrain telescopes. Dielectric coatings are also much more resistant to scratches and degradation over time.
Each optical set is thoroughly tested by the manufacturer.
For consistant quality each optical set is tested and hand-corrected after the automatic production with state-of-the-art machinery. Final testing of the optical set is performed by laser interferometry. Collimation of the secondary and primary mirror set is also performed by laser interferometer during final stages of assembly.
Mechanical Advantages of the GSO RC Astrographs
– Fixed primary mirror cell and focusing by Crayford focuser eliminates image shift
– Computer-optimized baffle system to eliminate stray light.
