The Very Large Telescope (VLT) is an astronomical facility operated since 1998 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, they were the largest optical reflecting telescopes in the world. They are currently the third and fourth largest.
Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium. If the object lies outside the Earth's atmosphere, as in the case of stars and planets, the phenomenon is termed astronomical scintillation; for objects within the atmosphere, the phenomenon is termed terrestrial scintillation. As one of the three principal factors governing astronomical seeing, atmospheric scintillation is defined as variations in illuminance only.
Adaptive optics (AO) is a technique of precisely deforming a mirror in order to compensate for light distortion. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, in microscopy, optical fabrication and in retinal imaging systems to reduce optical aberrations. Adaptive optics works by measuring the distortions in a wavefront and compensating for them with a device that corrects those errors such as a deformable mirror or a liquid crystal array.
A collimated beam of light or other electromagnetic radiation has parallel rays, and therefore will spread minimally as it propagates. A laser is an archetypical example. A perfectly collimated light beam, with no divergence, would not disperse with distance. However, diffraction prevents the creation of any such beam.
In astronomy, seeing is the degradation of the image of an astronomical object due to turbulence in the atmosphere of Earth that may become visible as blurring, twinkling or variable distortion. The origin of this effect is rapidly changing variations of the optical refractive index along the light path from the object to the detector. Seeing is a major limitation to the angular resolution in astronomical observations with telescopes that would otherwise be limited through diffraction by the size of the telescope aperture. Today, many large scientific ground-based optical telescopes include adaptive optics to overcome seeing.
In astronomy, a guide star is a reference star used to accurately maintain the tracking by a telescope of a celestial body, whose apparent motion through the sky is primarily due to Earth's rotation.
Orbiter is a space flight simulator program developed to simulate spaceflight using realistic Newtonian physics. The simulator was released on 27 November 2000; the latest edition, labeled "Orbiter 2016", was released on 30 August 2016, the first new version of the simulator since 2010. On 27 July 2021, Dr Schweiger announced to the Orbiter Community that Orbiter is being published under open source MIT license.
Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical models. It is the practice and study of observing celestial objects with the use of telescopes and other astronomical instruments.
Lucky imaging is one form of speckle imaging used for astrophotography. Speckle imaging techniques use a high-speed camera with exposure times short enough so that the changes in the Earth's atmosphere during the exposure are minimal.
A laser guide star is an artificial star image created for use in astronomical adaptive optics systems, which are employed in large telescopes in order to correct atmospheric distortion of light. Adaptive optics (AO) systems require a wavefront reference source of light called a guide star. Natural stars can serve as point sources for this purpose, but sufficiently bright stars are not available in all parts of the sky, which greatly limits the usefulness of natural guide star adaptive optics. Instead, one can create an artificial guide star by shining a laser into the atmosphere. Light from the beam is reflected by components in the upper atmosphere back into the telescope. This star can be positioned anywhere the telescope desires to point, opening up much greater amounts of the sky to adaptive optics.
The 3.67 m Advanced Electro Optical System Telescope is a Department of Defense telescope at Haleakala Observatory. The telescope is part of the Maui Space Surveillance Complex (MSSC), which in turn is part of the Air Force Maui Optical and Supercomputing Site (AMOS).
The Dunn Solar Telescope also known as the Richard B. Dunn Solar Telescope is a unique vertical-axis solar telescope, in Sunspot, New Mexico located at Sacramento Peak, New Mexico. It is the main telescope at the Sunspot Solar Observatory, operated by New Mexico State University in partnership with the National Solar Observatory through funding by the National Science Foundation, the state of New Mexico and private funds from other partners. The Dunn Solar Telescope specializes in high-resolution imaging and spectroscopy to help astrophysicists worldwide obtain a better understanding of how the Sun affects the Earth. Completed in 1969, it was upgraded with high-order adaptive optics in 2004 and remains a highly versatile astrophysical observatory which serves as an important test platform for developing new instrumentation and technologies. The Dunn Solar Telescope, located in Sunspot, New Mexico, is a vertical-axis solar telescope that specializes in high-resolution imaging and spectroscopy. It was completed in 1969 and received a significant upgrade with high-order adaptive optics in 2004.
David L. Fried was an American scientist, best known for his contributions to optics. Fried described what has come to be known as the Fried Parameter, or r0. The Fried Parameter is a measure of the strength of the turbulence in the atmosphere of Earth. The turbulence causes what is known as seeing in astronomy and usually limits the optical resolution of ground-based telescopes and the detail in their images of astronomical objects. The Fried Parameter describes the smallest diameter of a telescope aperture at which the image fidelity starts to suffer significantly from turbulent airflows in the atmosphere of Earth. The Fried Parameter may change quickly on the time scale of minutes, or less. Typical values for the Fried Parameter in the visible spectrum may range from less than one centimeter to some tens of centimeters at good astronomical sites.
The C. Donald Shane telescope is a 120-inch (3.05-meter) reflecting telescope located at the Lick Observatory in San Jose, California. It was named after astronomer C. Donald Shane in 1978, who led the effort to acquire the necessary funds from the California Legislature, and who then oversaw the telescope's construction. It is the largest and most powerful telescope at the Lick Observatory, and was the second-largest optical telescope in the world when it was commissioned in 1959.
The Daniel K. Inouye Solar Telescope (DKIST) is a scientific facility for studies of the Sun at Haleakala Observatory on the Hawaiian island of Maui. Known as the Advanced Technology Solar Telescope (ATST) until 2013, it was named after Daniel K. Inouye, a US Senator for Hawaii. It is the world's largest solar telescope, with a 4-meter aperture. The DKIST is funded by National Science Foundation and managed by the National Solar Observatory. The total project cost is $344.13 million. It is a collaboration of numerous research institutions. Some test images were released in January 2020. The end of construction and transition into scientific observations was announced in November 2021.
Leibniz Institute for Astrophysics Potsdam (AIP) is a German research institute. It is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory Potsdam (AOP) founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP was founded in 1992, in a re-structuring following the German reunification.
ALPAO is a company which manufactures a range of adaptive optics products for use in research and industry, including deformable mirrors with large strokes, wavefront sensors, and adaptive optics loops. These products are designed for astronomy, vision science, microscopy, wireless optical communications, and laser applications.
Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT-SPHERE) is an adaptive optics system and coronagraphic facility at the Very Large Telescope (VLT). It provides direct imaging as well as spectroscopic and polarimetric characterization of exoplanet systems. The instrument operates in the visible and near infrared, achieving exquisite image quality and contrast over a small field of view around bright targets.
