Ritchey–Chrétien telescope

A reflecting telescope that uses hyperbolic primary and secondary mirrors to reduce coma and provide a wide, well-corrected field of view.

Hyperbolic mirror: A mirror whose reflecting surface follows a hyperboloid, a conic section that can be tailored to control optical aberrations. Both mirrors use hyperbolic surfaces, unlike the simpler mirror pair in a classical Cassegrain.
Reflecting telescope: A telescope that forms images primarily with reflective optical surfaces. The Ritchey–Chrétien belongs to this family and avoids chromatic aberration from powered lenses.
George Willis Ritchey: An American optician and astronomer who built large reflecting telescopes and co-developed the Ritchey–Chrétien design. Ritchey brought extensive experience in mirror making and large-telescope construction to the design.
Hubble Space Telescope: A space-based observatory launched in 1990 that observes the universe across ultraviolet, visible, and near-infrared wavelengths. Its primary and secondary mirrors form a Ritchey–Chrétien optical system.
Classical Cassegrain telescope: A Cassegrain telescope with a parabolic primary mirror and a hyperbolic secondary mirror. Its simpler mirror combination corrects spherical aberration but retains more coma off axis.
Coma (optics): An off-axis aberration that makes point sources appear comet-shaped in an optical system. The mirror shapes are chosen chiefly to eliminate this aberration over a broad field.
Conic section: A curve formed by intersecting a plane with a cone, including circles, ellipses, parabolas, and hyperbolas. Its mirror profiles are specified by conic sections, especially the hyperbola.
Henri Chrétien: A French astronomer and optical designer who co-developed the Ritchey–Chrétien telescope. Chrétien contributed the optical design that paired hyperbolic mirrors for improved off-axis imaging.
Very Large Telescope: The European Southern Observatory’s array of four 8.2-meter optical telescopes in Chile. Its Unit Telescopes use Ritchey–Chrétien optics for astronomical observations.
Dall–Kirkham telescope: A Cassegrain variant with an ellipsoidal primary mirror and a spherical secondary mirror. It is simpler to manufacture but generally offers a narrower well-corrected field.

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Spherical aberrationBroader topic: Its mirror shapes correct spherical aberration in a wide-field telescope system.