A primary mirror is the principal light-gathering surface of a reflecting telescope.
The Very Large Telescope (VLT) is a facility operated by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a primary mirror that measures 8.2 meters in diameter. These optical telescopes, named Antu, Kueyen, Melipal, and Yepun, are generally used separately but can be combined to achieve a very high angular resolution. The VLT array is also complemented by four movable Auxiliary Telescopes (ATs) with 1.8-meter apertures.
The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have 10 m (33 ft) aperture primary mirrors, and when completed in 1993 and 1996 were the largest optical reflecting telescopes in the world. They are currently the 3rd and 4th largest.
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.
An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through electronic image sensors.
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.
A Dobsonian telescope is an altazimuth-mounted Newtonian telescope design popularized by John Dobson in 1965 and credited with vastly increasing the size of telescopes available to amateur astronomers. Dobson's telescopes featured a simplified mechanical design that was easy to manufacture from readily available components to create a large, portable, low-cost telescope. The design is optimized for observing faint, deep-sky objects such as nebulae and galaxies. This type of observation requires a large objective diameter of relatively short focal length and portability for travel to less light-polluted locations.
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.
The Hale Telescope is a 200-inch (5.1 m), f/3.3 reflecting telescope at the Palomar Observatory in San Diego County, California, US, named after astronomer George Ellery Hale. With funding from the Rockefeller Foundation in 1928, he orchestrated the planning, design, and construction of the observatory, but with the project ending up taking 20 years he did not live to see its commissioning. The Hale was groundbreaking for its time, with double the diameter of the second-largest telescope, and pioneered many new technologies in telescope mount design and in the design and fabrication of its large aluminum coated "honeycomb" low thermal expansion Pyrex mirror. It was completed in 1949 and is still in active use.
The Giant Magellan Telescope (GMT) is a 25.4-meter, ground-based, extremely large telescope under construction at Las Campanas Observatory in Chile's Atacama Desert. Commissioning is anticipated in the late 2020s. Once complete, the Giant Magellan will be the largest Gregorian telescope ever built observing in optical and mid-infrared light. The telescope uses seven of the world’s largest mirrors to form a light collecting area of 368 square meters.
The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it will be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observatory (ESO) agency, it is located on top of Cerro Armazones in the Atacama Desert of northern Chile.
The BTA-6 is a 6-metre (20 ft) aperture optical telescope at the Special Astrophysical Observatory located in the Zelenchuksky District of Karachay-Cherkessia on the north side of the Caucasus Mountains in southern Russia.
The MMT Observatory (MMTO) is an astronomical observatory on the site of Fred Lawrence Whipple Observatory. The Whipple observatory complex is located on Mount Hopkins, Arizona, US in the Santa Rita Mountains. The observatory is operated by the University of Arizona and the Smithsonian Institution, and has a visitor center in nearby Amado, Arizona. The MMTO is the home of the MMT, which has a primary mirror 6.5 m in diameter. The name comes from the six smaller mirrors originally used before the single primary mirror was installed in 1998. The primary mirror has a special lightweight honeycomb design made by the University of Arizona's Steward Observatory Mirror Laboratory. The MMT is housed in a building which allows the walls and roof around the telescope to be completely rolled back, allowing it to cool down very quickly in order to improve observation.
A segmented mirror is an array of smaller mirrors designed to act as segments of a single large curved mirror. The segments can be either spherical or asymmetric. They are used as objectives for large reflecting telescopes. To function, all the mirror segments have to be polished to a precise shape and actively aligned by a computer-controlled active optics system using actuators built into the mirror support cell.
PLate OPtimizer, or PLOP is a CAD program used by amateur telescope makers to design primary mirror support cells for reflecting telescopes. It was developed by telescope maker David Lewis, first described in 1999, and used to simplify calculations needed in the design of mirror support cells. It was based on Toshimi Taki's 1993 program PLATE, with a simplified user interface, thus giving it wide acceptance among makers of large Dobsonian style amateur telescopes, with good support of mirrors as thin as two inches for a diameter of thirty inches.
In astronomy, a mirror support cell - more commonly mirror cell - is a component of a reflecting telescope that supports the mirror in place to hold optical alignment, allow collimation adjustment, and protect it from falling out. The common usage of the word denotes the cell that holds the primary mirror (M1), however technically it could also be used to denote the support assembly for the secondary mirror (M2) or other mirrors.
Optical Telescope Element (OTE) is a sub-section of the James Webb Space Telescope, a large infrared space telescope launched on 25 December 2021, consisting of its main mirror, secondary mirrors, the framework and controls to support the mirrors, and various thermal and other systems.
The ExoLife Finder (ELF) telescope is an under-development hybrid interferometric telescope being designed at the Instituto de Astrofisica de Canarias (IAC) for the direct detection and imaging of exoplanets and potentially water-bearing exoplanets. Developed by a collaboration of scientists and engineers including the PLANETS Foundation, the ELF aims to analyze the surfaces and atmospheres of exoplanets for evidence of life, focusing on nearby star systems within 25 light years of Earth. The telescope’s design features non-redundant circular arrays of 5-meter-scale mirrors and tensegrity-based mechanical support with an outer diameter of 35m. It uses multiple layers of advanced atmospheric wavefront sensing and control. It is a scalable optical concept, and could be built within a 10 year timeframe. A 3.5-meter precursor called the Small ELF (SELF) is currently being built in the Canary Islands. The ELF's first targets will include nearby stars cooler than the Sun.
