Ritchey Chretien carbon truss


This telescope was designed to produce better images over a large photographic field. Coma makes it harder to measure star positions, and the Ritchey-Chrétien is coma-free, producing round stars over the entire field. The hyperbolic surfaces on both mirrors are not for the faint of heart. These curves are hard to produce and test. Unless you plan on doing photography and measuring star positions (astrometry) there is little reason for choosing the difficulty of this design.

The degree of field curvature is related to the difference in radii between the primary and secondary mirrors. A system with a flat field is possible, but requires a very fast primary with a deep, difficult to figure curve. The short focal length of the primary then dictates a large secondary causing more than 50% central obstruction. The differece between a ritchey chretien and another lens. 

Modeling and Finite Element Analysis  


All mechanics are machined at CNC using aluminum 6061

T6 and finally completely anodized black and red.




Toscanoptics company for many years working on optical RC very carefully. Our mirrors are totally figured by hand and tested in controlled laboratory conditions. All series of primary mirrors for RC are processed at least 1/18 PTV -1/60  RMS.  So we get a value of the entire focal plane of at least 1/5-1/6 lambda - 1/40 RMS.


Each optic is supplied with test report.

Each secondary mirror is tested by interferometric test at 660nm

and finally in autocollimation with a flat reference.



Ritchey-Chretien truss Technical data

                                    RC 12.5"                      RC 16"                           RC 20"                         RC 24"                             




Primary mirror  dia.                       318mm                        410mm                           510mm                        610mm


Optical dia.                                     315mm                        408mm                           508mm                        608mm     


Primary mirror aperture                F/3                              F/3                                 F/3                               F/3


Equivalent focal                             F/9                              F/9                                  F/9                               F/9


Secondary mirror dia.                   120mm                        141mm                           185mm                         211mm


Obstruction                                    0.39%                            0.36%                              0.39%                            0.37%


Back focus                                      350mm                        350mm                          350mm                        350mm


Weight                                            26Kg                            43Kg                              73Kg                           120kg


Price €                                             8100,00                       15.780,00                       26.500,00                    56.200,00    


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Why Ritchey-Chretien carbon truss models


A Serrurier truss is used in telescope tube assembly construction. The design was created in 1935 by engineer Mark U. Serrurier when he was working on the Mount Palomar 200 in (5.1 m) Hale telescope.[1] The design solves the problem of truss flexing by supporting the primary objective mirror and the secondary mirror by two sets of opposing trusses before and after the declination pivot. The trusses are designed to have an equal amount of flexure, which allows the optics to stay on a common optical axis. When flexing, the "top" truss resists tension and the "bottom" truss resists compression. This has the effect of keeping the optical elements parallel to each other. The net result is all of the optical elements stay in collimation regardless of the orientation of the telescope.