RC Optical Systems 12.5" f/9 Ritchey-Chretien Carbon Fiber Optical Tube

Telescopes by RC Optical Systems are the lightest and most thermally stable in their class, bar none! Correct composite construction allows for "focus and forget" utilization. RCOS Ritchey-Chretiens maintain precise focus all night, every night. These are just a few reasons why they continue to be the World's #1 manufacturer of Ritchey-Chretien Telescopes.

RC Optical Systems selected the Ritchey-Chretien design for its wide coma free field of view. Designed principally as a photographic instrument by American George Ritchey and Frenchman Henri Chretien, the Ritchey-Chretien design is coma free. Coma is an aberration common in all reflecting telescope systems. The Ritchey-Chretien design utilizes a hyperbolic primary and secondary mirror, which correct for coma. The Ritchey-Chretien has the largest aberration-free field of view, of any reflecting telescope made.

The hyperbolic mirrors utilized in the Ritchey-Chretien design are very difficult to manufacture. However, given the benefits of the design, the Ritchey-Chretien has been the choice of nearly all professional observatories for the last 50 years.

RCOS uses only the finest optics available for their Ritchey-Chretien telescopes. They are manufactured by some of the most experienced opticians in the world, and are guaranteed to be at least 1/25th wave RMS. Final figuring is done by either computerized polishing or Ion Milling. All mirrors utilize zero expansion materials such as Astro-Sitall, Zerodur, or ULE. These materials ensure the mirror will maintain shape during changing temperatures. Interferometric testing and fringe analysis data is provided with every set of optics.

Amateurs and Professionals alike are now using larger format and higher resolution CCD cameras. In addition to its originally intended use as a photographic instrument, the Ritchey-Chretien has become the ultimate CCD imaging platform.

Everything RCOS manufactures is designed in CAD (Computer Aided Design). Every part and component is assembled in CAD before they start machining. Rather than a "trial and error" or "overkill to be sure" approach, RCOS designs, engineers, and models all of their critical components. This ensures that you get the best product or part for its intended purpose. For example, RC Optical needed a low frequency, high strength fork mount for their latest .6m class telescope. By engineering and modeling, they were able to get the frequency and flexure to remarkable limits!

Once the component is designed and modeled, it's machined out of solid T6-6061 (or 7075) Aluminum. All components are CNC Machined to ensure precision and repeatability.

The telescope and telescope tube also play a vital role. Everything matters. So RCOS carefully considered all aspects of the design to develop a system that functions to it's fullest potential.

Typical aluminum and fiberglass telescope tubes both have a high coefficient of expansion and unstable mirror spacing. Telescopes made of such products require frequent refocusing during the night as the temperature changes. As an example, a F/9 Cassegrain has a 9x affect in back focus relative to mirror spacing. That is, a 1x change in mirror spacing changes the back focus 9x. So, when the temperature changes, so does the telescope's focus.

Carbon does not suffer from these instability problems. That's why RCOS chose to use an optical tube made of carbon graphite fiber. Carbon has a very low coefficient of expansion and also has excellent thermal properties. Focus and forget. Night after night, month after month! RC Optical Systems was the first manufacturer to introduce commercially available Carbon Tubes / Carbon Trusses for telescopes, and they continue to be the world's largest manufacturer of Carbon Tube / Carbon Truss Ritchey-Chretien Telescopes!

Ask for Carbon only! Other manufacturers have since introduced carbon fiber tubes. Some of these other carbon tubes are made with a high epoxy content, fiberglass, layers of Styrofoam, or even metallic components. These additional materials are not consistent with the low expansion and thermal properties of carbon fiber and may even negate the reason for using carbon.

Cassegrains have a two mirror, amplified optical system. Mirror spacing and backfocus are directly related to each other. If you change one, it affects the other. Different accessories or cameras will change the backfocus, which will change the required mirror spacing.

Since an Ritchey-Chretien is part of the Cassegrain family, a secondary mirror focuser is required for optimum optical performance. All of RCOS telescopes are shipped with a secondary focuser as standard equipment. This secondary focuser is an original RCOS design that allows the secondary mirror to move in precise increments without backlash, wobble, or play. It is a true "zero image shift" focuser. The absolute precision is due to twin stainless steel linear races riding on 4 linear ball bearings. Solid and very, very precise.

Fixed Instruments Adapter Set
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• Eliminate focuser drift and flexure

• Added Bolt-on security for your expensive camera and accessories.

• Save weight

• Compatible with all Astro Physics Accessories

• Includes .75, 1.25, 1.75 and 2.5 inch spacers

• RC Optical Systems Fixed Instruments Adapter (FIA) is standard equipment on all new RCOS Telescopes

Shown on Mountain Instruments MI-250 Mount (sold separately)

Ritchey-Chretien 12.5" (0.32 meter) Specifications

• 12.5" F/9 Ritchey-Chretien Zero Expansion Astro-Sitall Optics certified to 1/25 wave RMS or better.

• Fringe analysis and interferometric data supplied with each optical set.

• Enhanced Aluminum (SiO2/TiO2) overcoat - 96.9% reflectivity.

• Low Expansion, light weight Carbon Fiber Tube for superior performance and stability.

• 6061 Aluminum Components - All CNC Machined.

• Precision Secondary Mirror Focuser.

• 2-Stage Primary mirror baffle with internal knife-edge light stops.

• Secondary light baffle.

• 6061 Aluminum Mounting Rings.

• 6061 Aluminum End Ring.

• Active Cooling.

• RCOS "Focus and Forget" Technology.

• Fully assembled, collimated, and ready to use when shipped in the Thermodyne Travel Case

• CNC Machined "light weight" dovetail plates - top and bottom.

• Losmandy RDF-90 Finder Scope 3-point mounting bracket.

• Fixed Instruments (rear cell) Adapter Set (FIA).

• Built in carbon dew shield.

• Tube end ring (aluminum).

• CNC machined dust cap.

• Diffuse Flat Field "Light Screen"

• Carbon Tube Length/Diameter: 41" (1041mm)/ 15.3" (389mm)

• Total Weight: 48 lbs. (21.8 kg.), including rings and dovetail plates

• System: 12.5" (318mm) f/9

• Primary Focal Length: 40" (1016mm)

• Back Focus: 12" (305mm)

• Secondary Amplification: 2.85X

• Primary to Secondary Spacing: 26.50" (673mm)

• Secondary Size: 4.8" (122mm)

• Primary Hole: 3.5" (89mm)

RC Optical Systems Product Number: RC12