A Ritchey–Chrétien telescope is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors (coma). The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; some well-known examples are the Hubble Space Telescope, the Keck telescopes and the ESO Very Large Telescope.
A reflecting telescope is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternative to the refracting telescope which, at that time, was a design that suffered from severe chromatic aberration. Although reflecting telescopes produce other types of optical aberrations, it is a design that allows for very large diameter objectives. Almost all of the major telescopes used in astronomy research are reflectors. Many variant forms are in use and some employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is sometimes referred to as a catoptric telescope.
The Newtonian telescope, also called the Newtonian reflector or just a Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton, using a concave primary mirror and a flat diagonal secondary mirror. Newton's first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope. The Newtonian telescope's simple design has made it very popular with amateur telescope makers.
In optics, the coma, or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration.
The Maksutov is a catadioptric telescope design that combines a spherical mirror with a weakly negative meniscus lens in a design that takes advantage of all the surfaces being nearly "spherically symmetrical". The negative lens is usually full diameter and placed at the entrance pupil of the telescope. The design corrects the problems of off-axis aberrations such as coma found in reflecting telescopes while also correcting chromatic aberration. It was patented in 1941 by Soviet optician Dmitri Dmitrievich Maksutov. Maksutov based his design on the idea behind the Schmidt camera of using the spherical errors of a negative lens to correct the opposite errors in a spherical primary mirror. The design is most commonly seen in a Cassegrain variation, with an integrated secondary, that can use all-spherical elements, thereby simplifying fabrication. Maksutov telescopes have been sold on the amateur market since the 1950s.
The Schmidt–Cassegrain is a catadioptric telescope that combines a Cassegrain reflector's optical path with a Schmidt corrector plate to make a compact astronomical instrument that uses simple spherical surfaces.
Celestron is a company that manufactures telescopes and distributes telescopes, binoculars, spotting scopes, microscopes, and accessories manufactured by its parent company, the Synta Technology Corporation of Taiwan.
The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas, the main characteristic being that the optical path folds back onto itself, relative to the optical system's primary mirror entrance aperture. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system.
Orion Telescopes & Binoculars is an American retail company that sells telescopes, binoculars and accessories online and in-store for astronomy and birdwatching. It was founded in 1975 and has corporate offices in Watsonville, California. A large proportion of its products are manufactured by the Chinese company Synta for the Orion brand name. Orion Telescopes & Binoculars ships its products to the United States and over 20 other countries. Orion puts out a semi-quarterly mail-order catalog as well as email catalogs. The company is a prominent advertiser in North American astronomy magazines, such as Sky & Telescope and Astronomy.
The following timeline lists the significant events in the invention and development of the telescope.
The ETX is a line of smaller aperture telescopes made by Meade Instruments.
TÜBİTAK National Observatory is a ground-based astronomical observatory operated by the TUG Institute of the Scientific and Technological Research Council of Turkey (TUBITAK). Established in 1991, it is located at an altitude of 2,450 m (8,040 ft) in Bakırtepe, around 50 km (31 mi) west-southwest of Antalya in southern Turkey.
The Meade LX90 is a Schmidt-Cassegrain design of telescope made by Meade Instruments for the mid-priced commercial telescope market. It uses a similar optical system to the bigger and more expensive Meade LX200—although it lacks some useful functions like primary mirror locking. The LX90 telescopes were equipped with Autostar soon after its 1999 introduction by Meade instruments. Optical apertures included in the product line included 8 (20 cm), 10 (25 cm) and 12 (30 cm) inches on a double tine fork mount and Autostar system.
Ursa Astronomical Association is the largest astronomical association in Finland. Ursa was founded on 2 November 1921. Founding members include a renowned Finnish astronomer Yrjö Väisälä. In 1926 Ursa established the Ursa Observatory in Kaivopuisto district of Helsinki. In 2007 the Tähtikallio Observatory & Education Center was established in Artjärvi, its current equipment includes an Astrofox 36" Folded Newtonian Open tube telescope, an Alluna 16" Ritchey-Chrétien telescope, a Meade 16" LX200GPS Schmidt-Cassegrain telescope, a Sky-Watcher ED 120mm refractor telescope fitted with a Baader AstroSolar Solar Filter and a piggybacked Coronado SolarMax 40 H-Alpha telescope. Ursa's primary functions include advancing amateur astronomy and astronomical education. They have also published a magazine Tähdet ja avaruus since 1971. Anyone can join Ursa for an annual fee.
The Givatayim Observatory is a public observatory that was founded in 1968 by the Israeli Astronomical Association and the Givatayim municipality.
The Heights Observatory is an Astronomical Observatory at The Heights School in Modbury Heights, Adelaide, South Australia.
RC Optical Systems was a high-end American telescope and optics manufacturer that specialized in Ritchey-Chrétien telescopes with hyperbolic mirrors. RC also made related mounts and systems for the telescopes, with a focus on open and closed carbon fiber trusses for low expansion. The basic Ritchey-Chrétien optical system uses two mirrors and no refracting elements, which reduces light loss and its optical characteristics make it popular for astrophotography. Refracting elements may be added to correct for field curvature.
The SUNY Oneonta Observatory is an astronomical observatory in Oneonta, New York, home to the state's largest optical telescope and one of the largest publicly open east of the Mississippi, a one-meter Newtonian reflector constructed by JMI Telescopes of Lakewood, Colorado.
The Meade LX200 is a family of commercial telescopes produced by Meade Instruments launched in 1992 with 8" (20.32 cm) and a 10" (25.4 cm) Schmidt–Cassegrain models on computerized altazimuth mounts. Two larger models, a 12" (30.48 cm) and a 16" (40.64 cm), quickly followed. The original version was later informally named the "classic" LX200 as newer upgraded versions replaced it. The first of these was the LX200GPS, which featured global positioning system electronics. A 360 mm (14 in) LX200GPS was later added to the line.
The ÇOMÜ Ulupınar Observatory (UPO) is a ground-based astronomical observatory, which was established in 2001 and formally opened on 19 May 2002. It is also known as Çanakkale Observatory or the University Observatory. The Ulupınar Observatory is part of the Çanakkale Onsekiz Mart University (ÇOMÜ) Faculty of Science and Arts.
