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Officina Stellare - Ultra CRC 250 Ritchey Chrètien telescope OTA

Model#: UCRC250OTA

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Manufactured by: Officina Stellare


Officina Stellare Ultra CRC 250

Move over Ritchey Chrètien designers... There's a new kid on the block and its name is Officina Stellare!    


The Officina Stellare Ultra CRC 250 telescope is a premier design. An ultra corrected Ritchey Chrètien telescope that features a unique and innovative primary cell design that includes a three fan ventilation system. Its beautiful zero expansion carbon fiber open truss tube body is trimmed with CNC aluminum fittings.


The Ultra CRC Series Ritchey Chrétien telescope made by Officina Stellare are built around the best quality optics today available. All optical sets are realized under precise quality requirement conditions, using the highest renewed standards in terms of quality of the materials being used and the production processes involved. Each optical set is provided with its own interferometry report stating and certifying the overall quality to the customer. In the making of the optics, Officina Stellare only use blanks of certified origin and perfect homogeneity. They offer, as a standard, very high reflectivity protected aluminizings and multi layer anti reflex coatings. It is possible to make special coatings (silver, gold etc.) for specific wavelength related needs. In addition, there is an in house, pneumatically insulated, 6 meters long and 500 Kg weight optical bench using a Zygo mark IV interferometer with phase shifter coupled with a highly sophisticated analysis software for producing extremely precise measurements and tests. Officina Stellare verifies each and every one of their instruments before delivery to the final user. 

Officina Stellare Ultra 250 telescope

The materials Officinia Stellare uses in their premium quality telescopes are mostly aluminum and carbon fiber because of their lightness, their mechanical and thermal properties and for the optimal resistance to environmental conditions. 

Officina Stellare telescope aluminum carbon fiberAll the mechanical parts for the the OTA are machined using CNC computer assisted machines and from a whole block of aluminum to guarantee the best possible precision. Also the carbon fiber components are produced following strict specification and tolerances. Each part has been computer designed and optimized for the best structural performance, rigidity and lightness. The holding systems for both mirrors, the spider, rings and all the structural components, even the smallest, are CNC machined from a single block of special aluminum (6061/7075, Ergal and Anticorodal), stainless steel, titanium and brass. The tubes are made of true carbon-graphite fiber obtained with the use of high vacuum process, allowing us to obtain the best stability of the focus vs temperature changes still maintaining the best structural rigidity and lightness. 

Great care is taken in the making of the rear holding cell of the primary mirror. The entire rear cell for the primary mirror is figured to have the best rigidity/weight ratio and for the fastest possible thermal stabilization between the environment and mirror. The convection and thermal irradiation are greatly improved with the use of three high quality axial fans in the back of the cell. 

Ultra CRC 250 telescope quality opticsGreat attention has been applied to simplify the collimation between the mirrors resulting in a stable, efficient but easy to use system. The collimation is accomplished by acting on just three points (the minimum required points to generate a single plane) using a special, great diameter preloaded bolts (one for each point). This results in a single hand use, simply turn the bolt left or right to move the mirror back and forth (no more complicated operations using push pull screws and locks) in a very intuitive way. Finding the correct positions is a snap. The mirror borders uses an opaque, circular mask to avoid any undesired light scattering. The light shields for the primary and secondary mirrors are computer designed and optimized to ensure complete illumination of the field still maintaining a complete protection from stray light. Inside the light shields there are also micro baffles that reduces, coupled with an opaque painting of the surfaces, to nearly zero any possible parasite stray light. In some cases and for particular applications, the light shield for the secondary mirror is made using a special layout that maintain the efficiency of the system while reducing the obstruction for the system. The back plate of our telescopes comes standard with a system for adjusting the planarity of the focal plane in order to compensate for any small misalignment in the imaging train, always unwanted and annoying specially on today’s large CCD cameras. 

Ultra CRC 250 optics telescope designThe Ultra Corrected Ritchey Chretien is an Officina Stellare exclusive optical scheme. Developed for highest photography performance and the highest efficiency of light transfer to focal plane, with only two hyperbolic mirrors and two spaced elements back group. The Officina Stellare Ultra CRC Series true carbon fiber/aluminum compound structure is designed and optimized with CAD and computer support modelling to achieve the best rigidity and lightness. The truss configuration made by using high vacuum production process, top quality and zero expansion carbon fiber tubes guarantee the greatest focus stability. Only special lightweight aluminum/Ergal alloy, stainless steel and brass metals are used. All parts are full CNC machined to guarantee the best possible precision. 


The Ritchey Cretien telescopic design provides superior and excellent elimiation of optical errors. In this design, coma abberation and other distortions are nearly absent. The Ultra CRC telescopes along with the other advancements provided by Officina Stellare such as the outer carbon fiber and aluminum exterior reduce the weight and volume for easier movement and convenience.


Ultra CRC is the achronym of Ultra Corrected Ritchey-Chrétien, the innovative Officina Stellare exclusive, 4 element optical design with fast focal ratio and flat field, representing the latest of many pioneering projects from Officina Stellare.Developed with in mind the highest possible photographic performanceswhile maintaining a high efficiency in transferringlight on the focal plane, the system consists of only two hyperbolic mirrors and a back end two element field corrector. According to the telescope model, the mirrors are produced with either near zero thermal expansion Sitall ceramic glass, or selected low expansion glasses. The corrected and illuminated field covers a diameter of over 60mm, with an outstanding performanceof less than 5 micron (1.0 micron RMS) stars at 30 mm from the optical axis, obtained at the fast F/5.4 focal ratio.


The native fast focal ratio of Ultra CRC astrographs allows to maintain extremely reduced the weight and the overall volume of optical tube.The innovative “double phase” light shield baffle on the secondary mirror is computer optimized with ray-tracing software and allows to eliminate the typical heavy light shield as well to minimize the central obstruction factor, increasing the quantity of light on the focal plane.The Officina Stellare Ultra CRC Series true carbon fiber/aluminum compound structure is designed and optimized with CAD and computer support modelling to achieve the best rigidity and lightness. The truss configuration made by using high vacuum production process, top quality and zero expansion carbon fiber tubes guarantee the greatest focus stability. Only special light weight aluminum/Ergal alloy, stainless steel and brass metals are used. All parts are full CNC machined to guarantee the best possible precision.The high resistance anodization is chosen for unbeatable resistance to environmental conditions. Our unique and innovative design of multipoint axial/radial support primary mirror cell as well the secondary mirror support guarantee absolutely no induced astigmatism on the mirrors and the total absence of mirror shift or flop. A simple to use, single movement operation, efficient and absolutely rock solid collimation system is present. To achieve the perfect collimation is now an extremely simple and immediate process. The Ultra CRC gives the astroimager a high extraction of the focal plane. This guarantees the installation of complex imaging trains, coupling CCD cameras, off-axis guiding systems, adaptive optics, filter wheels, etc., as requested by high level astroimaging tasks. The fastest possible thermal stabilization time is guaranteed, thanks to the mechanical design of the optical tube and to the presenceof three high quality fans.The mechanical design includes a standard four Losmandy dovetail side bars for mount interface and piggy-back guide scopes and/or accessories. Great attention is given to constructive details to complete this masterpiece: computer designed baffles, focal plane tilt adjusting, high precision spherical joint in the truss structure, double parallel split ring for the secondary mirror/spider support, radial micrometric adjusting of spider, manual or motorized zero shift secondary mirror movement, special opaque paint for all sensitive parts of the optical path.


Officina Stellare Ultra Corrected Ritchey Chrètien 250 Telescope Mechanical Detalls...

  • Compact and light: 580 mm length, 400 mm outside max diameter, 17 Kg weight.
  • State of art construction: full CNC machined aluminum parts and ultra rigid true carbon truss structure.
  • Computer designed and optimized, two stage, secondary mirror light shield for minimal obstruction.
  • Large focus extraction to allow the use of every imaging train.
  • Easy piggy pack of guiding or ancillary equipment thanks to standard four dovetail bar structure.




Additional Information

Name Officina Stellare - Ultra CRC 250 Ritchey Chrètien telescope OTA
Manufacturer Officina Stellare
Model UCRC250OTA
Aperture 250 mm
Diameter 250 mm (9.8")
Focal Length 1400 mm
Focal Ratio f/5.6
Optical Design Carbon truss with Sitall glass
Optical Tube Length 580 mm