Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, stars, nebulae and comets. More all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, the study of the Universe as a whole. Astronomy is one of the oldest of the natural sciences; the early civilizations in recorded history, such as the Babylonians, Indians, Nubians, Chinese and many ancient indigenous peoples of the Americas, performed methodical observations of the night sky. Astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, but professional astronomy is now considered to be synonymous with astrophysics. Professional astronomy is split into theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, analyzed using basic principles of physics.
Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain observational results and observations being used to confirm theoretical results. Astronomy is one of the few sciences in which amateurs still play an active role in the discovery and observation of transient events. Amateur astronomers have made and contributed to many important astronomical discoveries, such as finding new comets. Astronomy means "law of the stars". Astronomy should not be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now distinct. Both of the terms "astronomy" and "astrophysics" may be used to refer to the same subject. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties," while "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, dynamic processes of celestial objects and phenomena."
In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could be called astrophysics; some fields, such as astrometry, are purely astronomy rather than astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics" depending on whether the department is affiliated with a physics department, many professional astronomers have physics rather than astronomy degrees; some titles of the leading scientific journals in this field include The Astronomical Journal, The Astrophysical Journal, Astronomy and Astrophysics. In early historic times, astronomy only consisted of the observation and predictions of the motions of objects visible to the naked eye.
In some locations, early cultures assembled massive artifacts that had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye; as civilizations developed, most notably in Mesopotamia, Persia, China and Central America, astronomical observatories were assembled and ideas on the nature of the Universe began to develop. Most early astronomy consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, the nature of the Sun and the Earth in the Universe were explored philosophically; the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the Ptolemaic system, named after Ptolemy.
A important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians, who laid the foundations for the astronomical traditions that developed in many other civilizations. The Babylonians discovered. Following the Babylonians, significant advances in astronomy were made in ancient Greece and the Hellenistic world. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. In the 3rd century BC, Aristarchus of Samos estimated the size and distance of the Moon and Sun, he proposed a model of the Solar System where the Earth and planets rotated around the Sun, now called the heliocentric model. In the 2nd century BC, Hipparchus discovered precession, calculated the size and distance of the Moon and inven
Field of view
The field of view is the extent of the observable world, seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. In the context of human vision, the term "field of view" is only used in the sense of a restriction to what is visible by external apparatus, like when wearing spectacles or virtual reality goggles. Note that eye movements are allowed in the definition but do not change the field of view. If the analogy of the eye's retina working as a sensor is drawn upon, the corresponding concept in human is the visual field, it is defined as "the number of degrees of visual angle during stable fixation of the eyes". Note that eye movements are excluded in the definition. Different animals have different visual fields, among others, on the placement of the eyes. Humans have a over 210-degree forward-facing horizontal arc of their visual field, while some birds have a complete or nearly complete 360-degree visual field.
The vertical range of the visual field in humans is around 150 degrees. The range of visual abilities is not uniform across the visual field, varies from animal to animal. For example, binocular vision, the basis for stereopsis and is important for depth perception, covers 114 degrees of the visual field in humans; some birds have a scant 20 degrees of binocular vision. Color vision and the ability to perceive shape and motion vary across the visual field; the physiological basis for, the much higher concentration of color-sensitive cone cells and color-sensitive parvocellular retinal ganglion cells in the fovea – the central region of the retina, together with a larger representation in the visual cortex – in comparison to the higher concentration of color-insensitive rod cells and motion-sensitive magnocellular retinal ganglion cells in the visual periphery, smaller cortical representation. Since cone cells require brighter light sources to be activated, the result of this distribution is further that peripheral vision is much more sensitive at night relative to foveal vision.
Many optical instruments binoculars or spotting scopes, are advertised with their field of view specified in one of two ways: angular field of view, linear field of view. Angular field of view is specified in degrees, while linear field of view is a ratio of lengths. For example, binoculars with a 5.8 degree field of view might be advertised as having a field of view of 102 mm per meter. As long as the FOV is less than about 10 degrees or so, the following approximation formulas allow one to convert between linear and angular field of view. Let A be the angular field of view in degrees. Let M be the linear field of view in millimeters per meter. Using the small-angle approximation: A ≈ 360 ∘ 2 π ⋅ M 1000 ≈ 0.0573 × M M ≈ 2 π ⋅ 1000 360 ∘ ⋅ A ≈ 17.45 × A In machine vision the lens focal length and image sensor size sets up the fixed relationship between the field of view and the working distance. Field of view is the area of the inspection captured on the camera’s imager; the size of the field of view and the size of the camera’s imager directly affect the image resolution.
Working distance is the distance between the back of the target object. In remote sensing, the solid angle through which a detector element is sensitive to electromagnetic radiation at any one time, is called instantaneous field of view or IFOV. A measure of the spatial resolution of a remote sensing imaging system, it is expressed as dimensions of visible ground area, for some known sensor altitude. Single pixel IFOV is related to concept of resolved pixel size, ground resolved distance, ground sample distance and modulation transfer function. In astronomy, the field of view is expressed as an angular area viewed by the instrument, in square degrees, or for higher magnification instruments, in square arc-minutes. For reference the Wide Field Channel on the Advanced Camera for Surveys on the Hubble Space Telescope has a field of view of 10 sq. arc-minutes, the High Resolution Channel of the same instrument has a field of view of 0.15 sq. arc-minutes. Ground-based survey telescopes have much wider fields of view.
The photographic plates used by the UK Schmidt Telescope had a field of view of 30 sq. degrees. The 1.8 m Pan-STARRS telescope, with the most advanced digital camera to date has a field of view of 7 sq. degrees. In the near infra-red WFCAM on UKIRT has a field of view of 0.2 sq. degrees and the VISTA telescope has a field of view of 0.6 sq. degrees. Until digital cameras could only cover a small field of view compared to photographic plates, although they beat photographic plates in quantum efficiency
An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geophysical and volcanology are examples of disciplines for which observatories have been constructed. Observatories were as simple as containing an astronomical sextant or Stonehenge. Astronomical observatories are divided into four categories: space-based, ground-based, underground-based. Ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum. Most optical telescopes are housed within a dome or similar structure, to protect the delicate instruments from the elements. Telescope domes have a slit or other opening in the roof that can be opened during observing, closed when the telescope is not in use. In most cases, the entire upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky. Radio telescopes do not have domes.
For optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution. The ideal locations for modern observatories are sites that have dark skies, a large percentage of clear nights per year, dry air, are at high elevations. At high elevations, the Earth's atmosphere is thinner, thereby minimizing the effects of atmospheric turbulence and resulting in better astronomical "seeing". Sites that meet the above criteria for modern observatories include the southwestern United States, Canary Islands, the Andes, high mountains in Mexico such as Sierra Negra. A newly emerging site which should be added to this list is Mount Gargash. With an elevation of 3600 m above sea level, it is the home to the Iranian National Observatory and its 3.4m INO340 telescope. Major optical observatories include Mauna Kea Observatory and Kitt Peak National Observatory in the US, Roque de los Muchachos Observatory and Calar Alto Observatory in Spain, Paranal Observatory in Chile.
Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the central part of Eastern Antarctica. This location provides the least atmospheric disturbances and best visibility. Beginning in 1930s, radio telescopes have been built for use in the field of radio astronomy to observe the Universe in the radio portion of the electromagnetic spectrum; such an instrument, or collection of instruments, with supporting facilities such as control centres, visitor housing, data reduction centers, and/or maintenance facilities are called radio observatories. Radio observatories are located far from major population centers to avoid electromagnetic interference from radio, TV, other EMI emitting devices, but unlike optical observatories, radio observatories can be placed in valleys for further EMI shielding; some of the world's major radio observatories include the Socorro, in New Mexico, United States, Jodrell Bank in the UK, Arecibo in Puerto Rico, Parkes in New South Wales and Chajnantor in Chile.
Since the mid-20th century, a number of astronomical observatories have been constructed at high altitudes, above 4,000–5,000 m. The largest and most notable of these is the Mauna Kea Observatory, located near the summit of a 4,205 m volcano in Hawaiʻi; the Chacaltaya Astrophysical Observatory in Bolivia, at 5,230 m, was the world's highest permanent astronomical observatory from the time of its construction during the 1940s until 2009. It has now been surpassed by the new University of Tokyo Atacama Observatory, an optical-infrared telescope on a remote 5,640 m mountaintop in the Atacama Desert of Chile; the oldest proto-observatories, in the sense of a private observation post, Wurdi Youang, Australia Zorats Karer, Armenia Loughcrew, Ireland Newgrange, Ireland Stonehenge, Great Britain Quito Astronomical Observatory, located 12 minutes south of the Equator in Quito, Ecuador. Chankillo, Peru El Caracol, Mexico Abu Simbel, Egypt Kokino, Republic of Macedonia Observatory at Rhodes, Greece Goseck circle, Germany Ujjain, India Arkaim, Russia Cheomseongdae, South Korea Angkor Wat, CambodiaThe oldest true observatories, in the sense of a specialized research institute, include: 825 AD: Al-Shammisiyyah observatory, Iraq 869: Mahodayapuram Observatory, India 1259: Maragheh observatory, Iran 1276: Gaocheng Astronomical Observatory, China 1420: Ulugh Beg Observatory, Uzbekistan 1442: Beijing Ancient Observatory, China 1577: Constantinople Observatory of Taqi ad-Din, Turkey 1580: Uraniborg, Denmark 1581: Stjerneborg, Denmark 1642: Panzano Observatory, Italy 1642: Round Tower, Denmark 1633: Leiden Observatory, Netherlands 1667: Paris Observatory, France 1675: Royal Greenwich Observatory, England 1695: Sukharev Tower, Russia 1711: Berlin Observatory, Germany 1724: Jantar Mantar, India 1753: Stockholm Observatory, Sweden 1753: Vilnius University Observatory, Lithuania 1753: Navy Royal Institute and Observatory, Spain 1759: Trieste Observatory, Italy 1757: Macfarlane Observatory, Scotland 1759: Turin Observatory, Italy 1764: Brera Astronomical Observatory, Italy 1765: Mohr Observatory, Indonesia 1774: Vatican Observatory, Vatican 1785: Dunsink Observatory, Ireland 1786: Madras Observatory, India 1789: Armagh Observatory, Northern Ireland 1790: Real Observatorio de Madrid, Spain, 1803: National Astronomical Observatory, Bogotá, Colombia.
1811: Tartu Old Observatory, Estonia 1812: Astronomical Observatory of Capodimonte, Italy 1830/1842: Depot of Charts & Instruments
Tenerife is the largest and most populated island of the seven Canary Islands. It is the most populated island of Spain, with a land area of 2,034.38 square kilometres and 904,713 inhabitants, 43 percent of the total population of the Canary Islands. Tenerife is the largest and most populous island of Macaronesia. Five million tourists visit Tenerife each year, the most visited island of the archipelago, it is one of the most important tourist destinations in the world. Tenerife hosts one of the world's largest carnivals and the Carnival of Santa Cruz de Tenerife is working to be designated UNESCO Intangible Cultural Heritage of the World. Tenerife is served by Tenerife-North Airport and Tenerife-South Airport. Tenerife is the economic capital of the Canary Islands; the capital of the island, Santa Cruz de Tenerife, is the seat of the island council. The city is capital of the autonomous community of Canary Islands, sharing governmental institutions such as presidency and ministries. Between the 1833 territorial division of Spain and 1927, Santa Cruz de Tenerife was the sole capital of the Canary Islands.
In 1927 the Crown ordered that the capital of the Canary Islands be shared, as it remains at present. Santa Cruz contains the modern Auditorio de Tenerife, the architectural symbol of the Canary Islands; the island is home to the University of La Laguna. The city of La Laguna is a UNESCO World Heritage Site, it is the second city most populated on the third in the archipelago. It was capital of the Canary Islands before Santa Cruz replaced it in 1833. Teide National Park is a UNESCO World Heritage Site and is located in the center of the island. In it, the Mount Teide rises as the highest elevation of Spain, the highest of the islands of the Atlantic Ocean, the third-largest volcano in the world from its base. On the island, the Macizo de Anaga has been a UNESCO Biosphere Reserve since 2015, it has the largest number of endemic species in Europe. The island's indigenous people, the Guanche Berbers, referred to the island as Achinet or Chenet in their language. According to Pliny the Younger, Berber king Juba II sent an expedition to the Canary Islands and Madeira.
Juba II and Ancient Romans referred to the island of Tenerife as Nivaria, derived from the Latin word nix, meaning snow, referring to the snow-covered peak of the Teide volcano. Maps dating to the 14th and 15th century, by mapmakers such as Bontier and Le Verrier, refer to the island as Isla del Infierno meaning "Island of Hell," referring to the volcanic activity and eruptions of Mount Teide; the Benahoaritas are said to have named the island, deriving it from the words ife. After colonisation, the Hispanisation of the name resulted in adding the letter "r" to unite both words, producing Tenerife. However, throughout history there have been other explanations to reveal the origin of the name of the island. For example, the 18th-century historians Juan Núñez de la Peña and Tomás Arias Marín de Cubas, among others, state that the island was named by natives for the legendary Guanche king, nicknamed "the Great." He ruled the entire island in the days before the conquest of the Canary Islands by Castilla.
The formal demonym used to refer to the people of Tenerife is Tinerfeño/a. In modern society, the latter term is applied only to inhabitants of the capital, Santa Cruz; the term "chicharrero" was once a derogatory term used by the people of La Laguna when it was the capital, to refer to the poorer inhabitants and fishermen of Santa Cruz. The fishermen caught mackerel and other residents ate potatoes, assumed to be of low quality by the elite of La Laguna; as Santa Cruz grew in commerce and status, it replaced La Laguna as capital of Tenerife in 1833 during the reign of Fernando VII. The inhabitants of Santa Cruz used the former insult to identify as residents of the new capital, at La Laguna's expense; the earliest known human settlement in the islands date to around 200 BC, by Berbers known as the Guanches. However, the Cave of the Guanches in the municipality of Icod de los Vinos in the north of Tenerife, has provided the oldest chronologies of the Canary Islands, with dates around the sixth century BC.
Regarding the technological level, the Guanches can be framed among the peoples of the Stone Age, although this terminology is rejected due to the ambiguity that it presents. The Guanche culture is characterized by an advanced cultural development related to the Berber cultural features imported from North Africa and a poor technological development, determined by the scarcity of raw materials minerals that allow the extraction of metals; the main activity was grazing, although the population were engaged in agriculture, as well as fishing and the collection of shellfish from the shore or using fishing craft. As for beliefs, the Guanche religion was polytheistic. Beside him there was an animistic religiosity that sacralized certain places rocks and mountains. Among the main Guanche gods could be highlighted. Singular was the cult to the dead, practi
A refracting telescope is a type of optical telescope that uses a lens as its objective to form an image. The refracting telescope design was used in spy glasses and astronomical telescopes but is used for long focus camera lenses. Although large refracting telescopes were popular in the second half of the 19th century, for most research purposes the refracting telescope has been superseded by the reflecting telescope which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of the objective lens by that of the eyepiece. Refractors were the earliest type of optical telescope; the first practical refracting telescopes appeared in the Netherlands about 1608, were credited to three individuals, Hans Lippershey and Zacharias Janssen, spectacle-makers in Middelburg, Jacob Metius of Alkmaar. Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo communicated the details of his invention to the public, presented the instrument itself to the Doge Leonardo Donato, sitting in full council.
All refracting telescopes use the same principles. The combination of an objective lens 1 and some type of eyepiece 2 is used to gather more light than the human eye is able to collect on its own, focus it 5, present the viewer with a brighter and magnified virtual image 6; the objective in a refracting telescope bends light. This refraction causes parallel light rays to converge at a focal point; the telescope converts a bundle of parallel rays to make an angle α, with the optical axis to a second parallel bundle with angle β. The ratio β/α is called the angular magnification, it equals the ratio between the retinal image sizes obtained without the telescope. Refracting telescopes can come in many different configurations to correct for image orientation and types of aberration; because the image was formed by the bending of light, or refraction, these telescopes are called refracting telescopes or refractors. The design Galileo Galilei used in 1609 is called a Galilean telescope, it used a divergent eyepiece lens.
A Galilean telescope, because the design has no intermediary focus, results in a non-inverted and upright image. Galileo's best telescope magnified objects about 30 times; because of flaws in its design, such as the shape of the lens and the narrow field of view, the images were blurry and distorted. Despite these flaws, the telescope was still good enough for Galileo to explore the sky; the Galilean telescope could view the phases of Venus, was able to see craters on the Moon and four moons orbiting Jupiter. Parallel rays of light from a distant object would be brought to a focus in the focal plane of the objective lens; the eyepiece lens renders them parallel once more. Non-parallel rays of light from the object traveling at an angle α1 to the optical axis travel at a larger angle after they passed through the eyepiece; this leads to an increase in the apparent angular size and is responsible for the perceived magnification. The final image is a virtual image, is the same way up as the object.
The Keplerian telescope, invented by Johannes Kepler in 1611, is an improvement on Galileo's design. It uses a convex lens as the eyepiece instead of Galileo's concave one; the advantage of this arrangement is that the rays of light emerging from the eyepiece are converging. This allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted. Higher magnifications can be reached with this design, but to overcome aberrations the simple objective lens needs to have a high f-ratio; the design allows for use of a micrometer at the focal plane. The achromatic refracting lens was invented in 1733 by an English barrister named Chester Moore Hall, although it was independently invented and patented by John Dollond around 1758; the design overcame the need for long focal lengths in refracting telescopes by using an objective made of two pieces of glass with different dispersion,'crown' and'flint glass', to limit the effects of chromatic and spherical aberration.
Each side of each piece is ground and polished, the two pieces are assembled together. Achromatic lenses are corrected to bring two wavelengths into focus in the same plane; the era of the'great refractors' in the 19th century saw large achromatic lenses culminating with the largest achromatic refractor built, the Great Paris Exhibition Telescope of 1900. Apochromatic refractors have objectives built with extra-low dispersion materials, they are designed to bring three wavelengths into focus in the same plane. The residual color error can be up than that of an achromatic lens; such telescopes contain elements of fluorite or special, extra-low dispersion glass in the objective and produce a crisp image, free of chromatic aberration. Due to the special materials needed in the fabrication, apochromatic refractors are more expensive than telescopes of other types with a comparable aperture. Refractors suffer from residual spherical aberration; this affects shorter focal ratios more than longer ones.
A robotic telescope is an astronomical telescope and detector system that makes observations without the intervention of a human. In astronomical disciplines, a telescope qualifies as robotic if it makes those observations without being operated by a human if a human has to initiate the observations at the beginning of the night, or end them in the morning, it may have software agent using Artificial Intelligence that assist in various ways such as automatic scheduling. A robotic telescope is distinct from a remote telescope, though an instrument can be both robotic and remote. Robotic telescopes are complex systems that incorporate a number of subsystems; these subsystems include devices that provide telescope pointing capability, operation of the detector, control of the dome or telescope enclosure, control over the telescope's focuser, detection of weather conditions, other capabilities. These varying subsystems are presided over by a master control system, always a software component. Robotic telescopes operate under closed loop or open loop principles.
In an open loop system, a robotic telescope system points itself and collects its data without inspecting the results of its operations to ensure it is operating properly. An open loop telescope is sometimes said to be operating on faith, in that if something goes wrong, there is no way for the control system to detect it and compensate. A closed loop system has the capability to evaluate its operations through redundant inputs to detect errors. A common such input would be position encoders on the telescope's axes of motion, or the capability of evaluating the system's images to ensure it was pointed at the correct field of view when they were exposed. Most robotic telescopes are small telescopes. While large observatory instruments may be automated, few are operated without attendants. Robotic telescopes were first developed by astronomers after electromechanical interfaces to computers became common at observatories. Early examples were expensive, had limited capabilities, included a large number of unique subsystems, both in hardware and software.
This contributed to a lack of progress in the development of robotic telescopes early in their history. By the early 1980s, with the availability of cheap computers, several viable robotic telescope projects were conceived, a few were developed; the 1985 book, Microcomputer Control of Telescopes, by Mark Trueblood and Russell M. Genet, was a landmark engineering study in the field. One of this book's achievements was pointing out many reasons, some quite subtle, why telescopes could not be reliably pointed using only basic astronomical calculations; the concepts explored in this book share a common heritage with the telescope mount error modeling software called Tpoint, which emerged from the first generation of large automated telescopes in the 1970s, notably the 3.9m Anglo-Australian Telescope. Since the late 1980s, the University of Iowa has been in the forefront of robotic telescope development on the professional side; the Automated Telescope Facility, developed in the early 1990s, was located on the roof of the physics building at the University of Iowa in Iowa City.
They went on to complete the Iowa Robotic Observatory, a robotic and remote telescope at the private Winer Observatory in 1997. This system observed variable stars and contributed observations to dozens of scientific papers. In May 2002, they completed the Rigel Telescope; the Rigel was a 0.37-meter F/14 built by Optical Mechanics, Inc. and controlled by the Talon program. Each of these was a progression toward utilitarian observatory. One of the largest current networks of robotic telescopes is RoboNet, operated by a consortium of UK universities; the Lincoln Near-Earth Asteroid Research Project is another example of a professional robotic telescope. LINEAR's competitors, the Lowell Observatory Near-Earth-Object Search, Catalina Sky Survey and others, have developed varying levels of automation. In 2002, the RAPid Telescopes for Optical Response project pushed the envelope of automated robotic astronomy by becoming the first autonomous closed–loop robotic telescope. RAPTOR was designed in 2000 and began full deployment in 2002.
Theproject was headed by Tom Vestrand and his team: James Wren, Robert White, P. Wozniak, Heath Davis, its first light on one of the wide field instruments was in late 2001, with the second wide field system came online in late 2002. Closed loop operations began in 2003; the goal of RAPTOR was to develop a system of ground-based telescopes that would reliably respond to satellite triggers and more identify transients in real-time and generate alerts with source locations to enable follow-up observations with other, telescopes. It has achieved both of these goals quite successfully. Now RAPTOR has been re-tuned to be the key hardware element of the Thinking Telescopes Technologies Project, its new mandate will be the monitoring of the night sky looking for interesting and anomalous behaviors in persistent sources using some of the most advanced robotic software deployed. The two wide field systems are a mosaic of CCD cameras; the mosaic covers and area of 1500 square degrees to a depth of 12th magnitude.
Centered in each wide field array is a single fovea system with a field of view of 4 degrees and depth of 16th magnitude. The wide field systems are separated by a 38 km baseline. Supporting these wide field systems are two other operational telescopes; the first of these is a cataloging patrol instrument with a mosaic 16 square degree field of view down to 16 magnitude. The other system is a.4m OTA with a yielding a depth of 19-20th magnitude and a coverage
A telescope is an optical instrument that makes distant objects appear magnified by using an arrangement of lenses or curved mirrors and lenses, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. The first known practical telescopes were refracting telescopes invented in the Netherlands at the beginning of the 17th century, by using glass lenses, they were used for both terrestrial applications and astronomy. The reflecting telescope, which uses mirrors to collect and focus light, was invented within a few decades of the first refracting telescope. In the 20th century, many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s; the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei.
In the Starry Messenger, Galileo had used the term perspicillum. The earliest existing record of a telescope was a 1608 patent submitted to the government in the Netherlands by Middelburg spectacle maker Hans Lippershey for a refracting telescope; the actual inventor is unknown but word of it spread through Europe. Galileo heard about it and, in 1609, built his own version, made his telescopic observations of celestial objects; the idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs and several attempts to build reflecting telescopes. In 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector; the invention of the achromatic lens in 1733 corrected color aberrations present in the simple lens and enabled the construction of shorter, more functional refracting telescopes.
Reflecting telescopes, though not limited by the color problems seen in refractors, were hampered by the use of fast tarnishing speculum metal mirrors employed during the 18th and early 19th century—a problem alleviated by the introduction of silver coated glass mirrors in 1857, aluminized mirrors in 1932. The maximum physical size limit for refracting telescopes is about 1 meter, dictating that the vast majority of large optical researching telescopes built since the turn of the 20th century have been reflectors; the largest reflecting telescopes have objectives larger than 10 m, work is underway on several 30-40m designs. The 20th century saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays; the first purpose built radio telescope went into operation in 1937. Since a large variety of complex astronomical instruments have been developed; the name "telescope" covers a wide range of instruments. Most detect electromagnetic radiation, but there are major differences in how astronomers must go about collecting light in different frequency bands.
Telescopes may be classified by the wavelengths of light they detect: X-ray telescopes, using shorter wavelengths than ultraviolet light Ultraviolet telescopes, using shorter wavelengths than visible light Optical telescopes, using visible light Infrared telescopes, using longer wavelengths than visible light Submillimetre telescopes, using longer wavelengths than infrared light Fresnel Imager, an optical lens technology X-ray optics, optics for certain X-ray wavelengthsAs wavelengths become longer, it becomes easier to use antenna technology to interact with electromagnetic radiation. The near-infrared can be collected much like visible light, however in the far-infrared and submillimetre range, telescopes can operate more like a radio telescope. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, but uses a parabolic aluminum antenna. On the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the frequency range from about 0.2 μm to 1.7 μm.
With photons of the shorter wavelengths, with the higher frequencies, glancing-incident optics, rather than reflecting optics are used. Telescopes such as TRACE and SOHO use special mirrors to reflect Extreme ultraviolet, producing higher resolution and brighter images than are otherwise possible. A larger aperture does not just mean that more light is collected, it enables a finer angular resolution. Telescopes may be classified by location: ground telescope, space telescope, or flying telescope, they may be classified by whether they are operated by professional astronomers or amateur astronomers. A vehicle or permanent campus containing one or more telescopes or other instruments is called an observatory. An optical telescope gathers and focuses light from the visible part of the electromagnetic spectrum. Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. In order for the image to be observed, photographed and sent to a computer, telescopes work by employing one or