The Cassegrain system dates back to 1672; over those three centuries, is was modified many times. One of such modifications resulted in a large undistorted field of view, which is especially important for photography of celestial objects.
Authors of this system, American astronomer George Ritchey and French optician A. Cretien in the first half of the 20th century suggested using hyperbolical primary and secondary mirrors.
Since that time, the Ritchey-Cretien system has been generally accepted by both professional astronomers and amateurs striving for high quality astronomical photographs.
Only few manufacturing companies in the world offer such optics to amateur astronomers, because manufacturing of mirrors with hyperbolical surfaces is a complex process, and thus, the cost of such telescopes is considerably higher than that of regular Newtonians and Cassegrains.
In Russia, such optics has been manufactured for 10 years by Novosibirsk company ASTROSIB (Director General and Head Constructor Anton Saveliev).
ASTROSIB’s two main Ritchey-Cretien system models, 250 mm (10”) and 360 mm (14”) telescopes, enjoy world-wide recognition, and fantastic photos made with the help of these telescopes are published in journals on Astronomy and in the Internet.