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Eight Inch refracting telescope.

An optical telescope is a telescope which is used to gather and focus light mainly from the visible part of the electromagnetic spectrum, for directly viewing a magnified image, making a photograph, etc. The term is used especially for a monocular with static mounting for observing the sky. Handheld binoculars are common for other purposes. Professional telescopes often focus the light onto electronic image sensors. Image File history File links Question_book-3. ... Download high resolution version (480x640, 140 KB)Eight Inch refracting telescope. ... Download high resolution version (480x640, 140 KB)Eight Inch refracting telescope. ... This article does not cite any references or sources. ... An image that is partially in focus, but mostly out of focus in varying degrees. ... “Visible light” redirects here. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... Magnification is the process of enlarging something only in appearance, not physical size. ... This article or section does not adequately cite its references or sources. ... A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and prisms; the use of prisms results in a lightweight telescope. ... Porro-prism binoculars with central focusing Binocular telescopes, or binoculars, (also known as field glasses) are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. ... A dismantled USB webcam, with and without a lens over its (Bayer format) image sensor. ...

There are three primary types of optical telescope: Refractors (Dioptrics) which use lenses, Reflectors (Catoptrics) which use mirrors, and Combined Lens-Mirror Systems (Catadioptrics) which use lenses and mirrors in combination (for example the Maksutov telescope and the Schmidt camera). The 50 cm refractor at Nice Observatory. ... Categories: Wikipedia cleanup | Telescopes | Astronomy stubs ... This article is about the optical device. ... Ritchey 24 reflecting telescope A reflecting telescope (reflector) is an optical telescope which uses mirrors, rather than lenses, to reflect light. ... This article belongs in one or more categories. ... A mirror, reflecting a vase. ... A catadioptric sensor is a visual sensor that contains mirrors (catoptrics) and lenses (dioptrics). ... A catadioptric sensor is a visual sensor that contains mirrors (catoptrics) and lenses (dioptrics). ... A 150mm aperture Maksutov-Cassegrain telescope. ... Optical ray paths inside Schmidt camera 2m Schmidt Camera (Alfred-Jensch-Telescope Tautenburg, Thuringia, Germany A Schmidt camera is an astronomical camera designed to provide wide fields of view with limited aberrations. ...

History

Main article: History of telescopes

The first telescopes may have been the Nimrud lens, by the ancient Assyrians, but the Visby lenses tentatively suggest that the technology was known to the Arabs and Persians. Leonard Digges is sometimes credited with the invention in England in the 1570s, but usually credit for assembling the first telescope is given to an unknown Dutch spectacle maker in about 1608. Some name that person as Hans Lippershey (c. 1570 – c. 1619), but Jacob Metius and Zacharias Jansen also claimed to have invented a telescope during the same period. Even if Lippershey did not make the first one, he publicized it. Galileo Galilei made his own telescope in 1609, calling it at first a "perspicillum," and then using the terms "telescopium" in Latin and "telescopio" in Italian (from which the English word derives). Galileo is generally credited with being the first to use a telescope for astronomical purposes. (Also the telescope was first used to spot ships.) Galileo's telescope consisted of a convex object lens and a concave eye lens, which is universally called a Galilean telescope (used as a viewfinder in many simple cameras). Later, Johannes Kepler described the optics of lenses (see his books Astronomiae Pars Optica and Dioptrice), including a new kind of astronomical telescope with two convex lenses (a principle often called the Kepler telescope). This article or section is not written in the formal tone expected of an encyclopedia article. ... The Nimrud lens is a piece of rock crystal, 3000 years old, and unearthed in Assyria-proper by Austen Henry Layard. ... The Visby lenses are ten lens-shaped rock crystals found in a viking grave in Gotland dating from the 10th century. ... Languages Arabic other minority languages Religions Predominantly Sunni Islam, as well as Shia Islam, Greek Orthodoxy, Greek Catholicism, Roman Catholicism, Alawite Islam, Druzism, Ibadi Islam, and Judaism Footnotes a Mainly in Antakya. ... The Persians of Iran (officially named Persia by West until 1935 while still referred to as Persia by some) are an Iranian people who speak Persian (locally named Fârsi by native speakers) and often refer to themselves as ethnic Iranians as well. ... Leonard Digges (1520 - 1559), father of Thomas Digges was a well-known mathematician and surveyor, credited to the invention of the theodolite and a great populariser of science through his publications in English. ... Events March 18 - Sissinios formally crowned Emperor of Ethiopia May 14 - Protestant Union founded in Auhausen. ... Hans Lippershey (1570–September 1619) was a Dutch lensmaker. ... Jacob (or Jacobus) Metius (died between 1624 and 1631), Dutch instrument-maker and optician. ... Zacharias Janssen (1580-1638) (flourished c. ... Galileo redirects here. ... // Events April 4 – King of Spain signs an edit of expulsion of all moriscos from Spain April 9 – Spain recognizes Dutch independence May 23 - Official ratification of the Second Charter of Virginia. ... Kepler redirects here. ... For the book by Sir Isaac Newton, see Opticks. ... This article is about the optical device. ...

How it works

For detailed information on specific designs of reflecting, refracting, and catadioptric telescopes see the main articles on Reflecting telescopes, Refracting telescopes, and Catadioptrics. A reflecting telescope (reflector) is an optical telescope which uses a combination of curved and plane (flat) mirrors to reflect light and form an image (catoptric), rather than lenses to refract or bend light to form an image (dioptric). ... Image of a refracting telescope from the Cincinnati Observatory in 1848 A refracting or refractor telescope is a dioptric telescope that uses a lens as its objective to form an image. ... Optical systems which involve both lenses and mirrors. ...

The basic scheme is that the primary light-gathering element, the objective (objective lens (1) or concave mirror), focuses light from a distant object (4) to a focal plane where it forms a real image (5). This image may be recorded, or viewed through an eyepiece (2) which acts like a magnifying glass. The eye (3) sees a magnified virtual image (6) at a large distance. An objective lens is the lens in a microscope, telescope, camera or other optical instrument, that receives the first light rays from the object being observed. ... A mirror, reflecting a vase. ... Top: The formation of a real image using a convex lens. ... A collection of different types of eyepieces. ... A magnifying glass is a single convex lens which is used to see girls better it is wonderful i love eating it is so tasty a mg is used also toproduce a magnified image of an object. ... Magnification is the process of enlarging something only in appearance, not physical size. ... Top: The formation of a virtual image using a concave lens. ...

Keplerian telescope, schematic

Telescopes which employ two convex lenses cause the image to appear inverted. These are referred to as inverting telescopes. Terrestrial versions of such telescopes and binoculars employ prisms (e.g. Porro prisms) or a relay lens between objective and eyepiece to invert the image once more. This can also be done with one convex lens and one concave lens (a Galilean telescope). Thus, an upright image appears in the eyepiece. These are referred to as erecting telescopes. Image File history File links Download high resolution version (1229x689, 17 KB) Description: Schematic drawing demonstrating how a telescope works (Keplerian or astronomical telescope) Source: Drawing created by myself as to test the drawing program of OpenOffice. ... Image File history File links Download high resolution version (1229x689, 17 KB) Description: Schematic drawing demonstrating how a telescope works (Keplerian or astronomical telescope) Source: Drawing created by myself as to test the drawing program of OpenOffice. ... Porro-prism binoculars with central focusing Binocular telescopes, or binoculars, (also known as field glasses) are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. ... In optics, a Porro prism, named for its inventor Ignazio Porro, is a type of reflection prism used in optical instruments to alter the orientation of an image. ...

Many types of telescope fold the optical path with secondary or tertiary mirrors. These may be integral part of the optical design (Cassegrain reflector and similar types), but also serve for making the telescope more compact and placing the eyepiece or detector at a more convenient position. On large telescopes these additional mirrors are often used to provide improved image quality over a larger field of view. The Forststernwarte Jena 50cm Cassegrain telescope. ...

Angular resolution

Ignoring blurring of the image by turbulence in the atmosphere (atmospheric seeing) and optical imperfections of the telescope, the angular resolution of an optical telescope is determined by the width of the objective, termed its "aperture" (the primary mirror, or lens.) The Rayleigh criterion for the resolution limit α_R (in radians) is given by Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... Angular resolution describes the resolving power of any optical device such as a telescope, a microscope, a camera, or an eye. ... a big (1) and a small (2) aperture For other uses, see Aperture (disambiguation). ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ... Some common angles, measured in radians. ...

α_R = 1.22λ / D,

where λ is the wavelength and D is the aperture. For visible light (λ = 550 nm), this equation can be rewritten: For other uses, see Wavelength (disambiguation). ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ...

α_R = 138 / D.

Here, α_R denotes the resolution limit in arcseconds and D is in millimeters. In the ideal case, the two components double stars can be split even if separated by slightly less than α_R. This is taken into account by the Dawes limit A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7. ... When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ...

α_D = 116 / D.

Essentially; the larger the aperture, the better the angular resolution

It should be noted that the resolution is NOT given by the maximum magnification (or "power") of a telescope. Telescopes marketed by giving high values of the maximum power often deliver poor images. Magnification is the process of enlarging something only in appearance, not physical size. ...

For large ground-based telescopes, the resolution is limited by atmospheric seeing. This limit can be overcome by placing the telescopes above the atmosphere, e.g., on the summits of high mountains, on balloon and high-flying airplanes, or in space. Resolution limits can also be overcome by adaptive optics or speckle imaging for ground-based telescopes. Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... A space observatory is any object in outer space which is used for observation of distant planets, galaxies, and other outer space objects. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... Speckle imaging (also known as video astronomy) describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add (image stacking) method or on speckle interferometry methods. ...

Recently, it has become practical to perform aperture synthesis with arrays optical telescopes. Very high resolution images can be obtained with groups of widely-spaced smaller telescopes, linked together by carefully-controlled optical paths, but these interferometers can only used for imaging bright objects such as stars or measuring the bright cores of active galaxies. Example images of starspots on Betelgeuse can be seen here. Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... This article or section does not cite its references or sources. ... An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. ... This article is about the star. ...

Focal length and f-ratio

The focal length determines how wide an angle the telescope can view with a given eyepiece or size of a CCD detector or photographic plate. The f-ratio (or focal ratio, or f-number) of a telescope is the ratio between the focal length and the aperture (i.e., diameter) of the objective. Thus, for a given aperture (light-gathering power), low f-ratios indicate wide fields of view. Wide-field telescopes (such as astrographs) are used to track satellites and asteroids, for cosmic-ray research, and for surveys of the sky. It is more difficult to reduce optical aberrations in telescopes with low f-ratio than in telescopes with larger f-ratio. A collection of different types of eyepieces. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ... Photographic plates were one of the earliest forms of photographic film, in which a light-sensitive emulsion of silver salts was applied to a glass plate. ... A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ... This article is about focal length related to lenses and systems of lenses. ... A 13-inch, f/5. ... For other uses, see Satellite (disambiguation). ... For other uses, see Asteroid (disambiguation). ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... This article or section is in need of attention from an expert on the subject. ...

Light-gathering power

The light-gathering power of an optical telescope is directly related to the diameter (or aperture) of the objective lens or mirror. Note that the area of a circle is proportional to the square of the radius. A telescope with a lens which has a diameter three times that of another will have nine times the light-gathering power. Larger objectives gather more light, and more sensitive imaging equipment can produce better images from less light. DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ...

Imperfect images

No telescope can form a perfect image. Even if a reflecting telescope could have a perfect mirror, or a refracting telescope could have a perfect lens, the effects of aperture diffraction could still not be escaped. In reality, perfect mirrors and perfect lenses do not exist, so image aberrations in addition to aperture diffraction must be taken into account. Image aberrations can be broken down into two main classes, monochromatic, and polychromatic. In 1857, Philipp Ludwig von Seidel (1821-1896) decomposed the first order monochromatic aberrations into five constituent aberrations. They are now commonly referred to as the five Seidel Aberrations. This article or section is in need of attention from an expert on the subject. ... Philipp Ludwig von Seidel (1821–1896) was a German mathematician. ...

The five Seidel aberrations

Spherical aberration 

The difference in focal length between paraxial rays and marginal rays, proportional to the square of the aperture.

Coma 

A most objectionable defect by which points are imaged as comet-like asymmetrical patches of light with tails, which makes measurement very imprecise. Its magnitude is usually deduced from the optical sine theorem.

Astigmatism 

The image of a point forms focal lines at the sagittal and tangiental foci and in between (in the absence of coma) an elliptical shape.

Curvature of Field

The Petzval curvature means that the image instead of lying in a plane actually lies on a curved surface which is described as hollow or round. This causes problems when a flat imaging device is used e.g. a photographic plate or CCD image sensor.

Distortion

Either barrel or pincushion, a radial distortion which must be corrected for if multiple images are to be combined (similar to stitching multiple photos into a panoramic photo).

They are always listed in the above order since this expresses their interdependence as first order aberrations via moves of the exit/entrance pupils. The first Seidel aberration, Spherical Aberration, is independent of the position of the exit pupil (as it is the same for axial and extra-axial pencils). The second, coma, changes as a function of pupil distance and spherical aberration, hence the well-known result that it is impossible to correct the coma in a lens free of spherical aberration by simply moving the pupil. Similar dependencies affect the remaining aberrations in the list. Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ... In optics (especially telescopes), the coma in an optical system refers to monochromatic aberration inherent to certain optical designs or due to imperfection in the lens or other components which results in off-axis point sources such as stars appearing distorted. ... In optics, the optical sine theorem states that the products of the index, height and sine of the slope angle of a ray in object space and its corresponding ray in image space are equal. ... In optics, astigmatism is when an optical system has different foci for rays that propagate in two perpendicular planes. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Panoramic photography is a style of photography that aims to create images with exceptionally wide fields of view, but has also come to refer to any photograph that is cropped to a relatively wide aspect ratio (see Panoramic format) While there is no formal definition for the point at which...

The chromatic aberrations

Longitudinal Chromatic Aberration

As with spherical aberration this is the same for axial and oblique pencils.

Transverse Chromatic Aberration (Chromatic Aberration of Magnification)

Optical Research telescopes

Harlan J. Smith Telescope at McDonald Observatory, Texas

Nearly all large research-grade astronomical telescopes are reflectors. Some reasons are: Image File history File links Download high resolution version (1704x2272, 928 KB) Inside the dome of the Harlan J. Smith Telescope, McDonald Observatory, Fort Davis, Texas, USA. Image taken by Daniel Schwen on Apr. ... Image File history File links Download high resolution version (1704x2272, 928 KB) Inside the dome of the Harlan J. Smith Telescope, McDonald Observatory, Fort Davis, Texas, USA. Image taken by Daniel Schwen on Apr. ... Link title ... McDonald Observatorys 2. ...

• In a lens the entire volume of material has to be free of imperfection and inhomogeneities, whereas in a mirror, only one surface has to be perfectly polished.
• Light of different colors travels through a medium other than vacuum at different speeds. This causes chromatic aberration.
• Reflectors work in a wider spectrum of light since certain wavelengths are absorbed when passing through glass elements like those found in a refractor or catadioptric.
• There are technical difficulties involved in manufacturing and manipulating large-aperture lenses. One of them is that all real materials sag in gravity. A lens can only be held by its perimeter. A mirror, on the other hand, can be supported by the whole side opposite to its reflecting face.

Most large research telescopes can operate as either a Cassegrain telescope (longer focal length, and a narrower field with higher magnification) or a Newtonian telescope (brighter field). They have a pierced primary mirror, a Newtonian focus, and a spider to mount a variety of replaceable secondary mirrors. Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. ... In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... Light path in a Cassegrain reflector Laurent Cassegrain was a catholic priest born in the region of Chartres around 1629 and died at Chaudon (Eure-et-Loir) on August 31, 1693. ... Newtonian Telescope The Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton (1643-1727), using a parabolic primary mirror and a flat diagonal secondary mirror. ...

A new era of telescope making was inaugurated by the Multiple Mirror Telescope (MMT), with a mirror composed of six segments synthesizing a mirror of 4.5 meters diameter. This has now been replaced by a single 6.5 m mirror. Its example was followed by the Keck telescopes with 10 m segmented mirrors. MMT can also refer to Methylcyclopentadienyl Manganese Tricarbonyl, an additive for automotive gasoline. ... This article is about the unit of length. ... The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ...

The largest current ground-based telescopes have a primary mirror of between 6 and 11 meters in diameter. In this generation of telescopes, the mirror is usually very thin, and is kept in an optimal shape by an array of actuators (see active optics). This technology has driven new designs for future telescopes with diameters of 30, 50 and even 100 meters. A primary mirror is a form of distributed data management on the Internet. ... Active optics is a relatively new technology for reflecting telescopes. ...

Relatively cheap, mass-produced ~2 meter telescopes have recently been developed and have made a significant impact on astronomy research. These allow many astronomical targets to be monitored continuously, and for large areas of sky to be surveyed. Many are robotic telescopes, computer controlled over the internet (see e.g. the Liverpool Telescope and the Faulkes Telescope North and South), allowing automated follow-up of astronomical events. A robotic telescope is an astronomical telescope and detector system that makes observations without the intervention of a human. ... The Liverpool Telescope is a 2m fully robotic telescope, meaning that it can be remotely operated and also run without human intervention once given a list of observations to make. ... The Faulkes Telescope North is a clone of the Liverpool Telescope, and is located at Haleakala Observatory. ... The Faulkes Telescope South is a clone of the Liverpool Telescope, and is located at Siding Spring Observatory. ...

Initially the detector used in telescopes was the human eye. Later, the sensitized photographic plate took its place, and the spectrograph was introduced, allowing the gathering of spectral information. After the photographic plate, successive generations of electronic detectors, such as the charge-coupled device (CCDs), have been perfected, each with more sensitivity and resolution, and often with a wider wavelength coverage. A detector is a device that detects or measures some phenomenon or stimulus, and produces some signal in response. ... For other uses, see Eye (disambiguation). ... Photographic plates were one of the earliest forms of photographic film, in which a light-sensitive emulsion of silver salts was applied to a glass plate. ... For Acoustic uses in spectrographs of sound waves, see below. ... A specially developed CCD used for ultraviolet imaging in a wire bonded package. ...

Current research telescopes have several instruments to choose from such as:

• imagers, of different spectral responses
• spectrographs, useful in different regions of the spectrum
• polarimeters, that detect light polarization.

The phenomenon of optical diffraction sets a limit to the resolution and image quality that a telescope can achieve, which is the effective area of the Airy disc, which limits how close two such discs can be placed. This absolute limit is called the diffraction limit (or sometimes the Rayleigh criterion, Dawes limit or Sparrow's resolution limit). This limit depends on the wavelength of the studied light (so that the limit for red light comes much earlier than the limit for blue light) and on the diameter of the telescope mirror. This means that a telescope with a certain mirror diameter can theoretically resolve up to a certain limit at a certain wavelength. For conventional telescopes on Earth, the diffraction limit is not relevant for telescopes bigger than about 10 cm. Instead, the seeing, or blur caused by the atmosphere, sets the resolution limit. But in space, or if adaptive optics are used, then reaching the diffraction limit is sometimes possible. At this point, if greater resolution is needed at that wavelength, a wider mirror has to be built or aperture synthesis performed using an array of nearby telescopes. In electrodynamics, polarization (also spelled polarisation) is the property of electromagnetic waves, such as light, that describes the direction of their transverse electric field. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... A computer-generated image of an Airy disc. ... Diffraction is the apparent bending and spreading of waves when they meet an obstruction. ... Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. ... Dawes limit is a formula to express the maximum resolving power of a microscope or telescope. ... DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). ... Schematic diagram illustrating how optical wavefronts from a distant star may be perturbed by a turbulent layer in the atmosphere. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ...

In recent years, a number of technologies to overcome the distortions caused by atmosphere on ground-based telescopes have been developed, with good results. See adaptive optics, speckle imaging and optical interferometry. Air redirects here. ... A deformable mirror can be used to correct wavefront errors in an astronomical telescope. ... Speckle imaging (also known as video astronomy) describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add (image stacking) method or on speckle interferometry methods. ... This article is in need of attention. ...

Famous optical telescopes

The Hubble Space Telescope orbits above Earth.

• The Hubble Space Telescope is in orbit beyond Earth's atmosphere to allow for observations not distorted by atmospheric seeing. In this way the images can be diffraction limited, and used for coverage in the ultraviolet (UV) and infrared. Also there is no background from light scattered by the air so very deep images are possible, despite the relatively small mirror size.
• The Keck telescopes are currently (as of 2006) the largest, but will soon be superseded by the Gran Telescopio Canarias.
• The Hobby-Eberly Telescope and Southern African Large Telescope are large 9.2 meter telescopes of a very different design. The mirror is held stationary and objects tracked by moving the instruments. This has significant operational restrictions, but gives a large aperture for a fraction of the cost of a fully steerable telescope.
• The Very Large Telescope array (VLT) at Paranal Observatory is currently (as of 2002) the record holder for total collecting area in an array of telescopes, with four telescopes each 8 meters in diameter. The four telescopes, belonging to the European Southern Observatory (ESO) and located in the Atacama desert in Chile, are usually operated independently for faint astronomical observations, but up to three telescopes can be operated together for aperture synthesis observations of bright objects.
• The Navy Prototype Optical Interferometer is the optical telescope (array) that can currently (as of 2005) produce the highest resolution images at visible wavelengths.
• The CHARA (Center for High Angular Resolution Astronomy) array is the telescope array that can currently (as of 2005) produce the highest resolution images at near-infrared wavelengths.
• There are many plans for even larger telescopes. One of them is the Overwhelmingly Large Telescope (OWL), which is intended to have a single aperture of 100 meters in diameter.
• The 200-inch (5.08-meter) Hale telescope on Palomar Mountain was the largest conventional research telescope for many years. It has a single borosilicate (Pyrex™) mirror that was famously difficult to construct. The mounting is a special design of equatorial mount called a yoke mount, which permits the telescope to be pointed at and near the north celestial pole.
• The 100-inch (2.54-meter) Hooker Telescope at the Mount Wilson Observatory was used by Edwin Hubble to discover galaxies and the redshift. The mirror was made of green glass by Saint-Gobain. In 1919, the telescope was used for the first stellar diameter measurements using interferometry. The telescope now has an adaptive optics system, and is still useful for advanced research.
• The 72-inch Leviathan at Birr Castle (in Ireland) was the largest telescope in the world from 1845 until it was dismantled in 1908. It was not exceeded in size until the construction of the Hooker Telescope.
• The 1.02-meter Yerkes Telescope (in Wisconsin) is the largest aimable refracting telescope in use.
• The Great Lick 36-inch (0.91 m) refractor built in 1889 at the Lick Observatory on Mt. Hamilton near San Jose, California.
• The 0.76-meter Nice refractor (in France) that became operational in 1888 was at that time the world's largest refractor. It was exceeded in size one year later; this was the last time the most powerful operational telescope in the world was located in Europe.
• The largest refractor ever constructed was French. It was on display at the 1900 Paris Exposition. Its lens was stationary, prefigured so as to sag into the correct shape. The telescope was aimed by the aid of a Foucault sidérostat, which is a movable plane mirror with a 2-meter diameter, mounted in a large cast-iron frame. The horizontal tube was 60 m long and the objective had 1.25 m in diameter. It was a failure.
• The Gran Telescopio CANARIAS (Grantecan, also GTC), is a high performance segmented 10.4 meter telescope that is being installed in one of the best sites of the Northern Hemisphere: the Roque de los Muchachos Observatory (La Palma, Canary Islands, Spain). As of July 2007, 12 of its 36 sub-mirrors are installed; when the remainder are installed it will be the world's largest.
• The 1-meter refracting Swedish Solar Telescope (SST) on La Palma (Spain), is currently the highest-resolution solar telescope in the world.
• The 26 inch refracting US Naval Observatory Telescope in Washington D.C. was used in the discovery of the two moons of Mars, Phobos and Deimos.

Image File history File links Download high resolution version (945x766, 76 KB) Hubble Space Telescope as seen from the Space Shuttle Discovery on mission STS-82. ... Image File history File links Download high resolution version (945x766, 76 KB) Hubble Space Telescope as seen from the Space Shuttle Discovery on mission STS-82. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... In astronomy, the seeing disk (seeing) is a reference to the best possible angular resolution which can be achieved by an optical telescope, which is viewing the celestial sphere from within an atmosphere. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... For other uses, see Ultraviolet (disambiguation). ... In astronomy, background commonly refers to the incoming light from an apparently empty part of the night sky. ... The Mauna Kea Observatory, an institute of the University of Hawaii, is considered one of the most important land-based observatories in the world for its isolated, unobstructed views of space without interference from man-made light sources. ... 2006 is a common year starting on Sunday of the Gregorian calendar. ... Gran Telescopio Canarias, 2006. ... The Hobby-Eberly Telescope is a 9. ... The Southern African Large Telescope (SALT) is a 10 metre (~32. ... One of the four telescopes that make up the VLT, named Kueyen. ... Paranal Observatory is an astronomical observatory located on Cerro Paranal (120 km south of Antofagasta) and operated by the European Southern Observatory. ... 2002 is a common year starting on Tuesday of the Gregorian calendar. ... This article is about the unit of length. ... The European Southern Observatory (ESO) is an international astronomical organisation, composed and supported by ten countries from the European Union plus Switzerland. ... Atacama Desert The Atacama Desert is a virtually rainless plateau in South America, extending 966 km (600 mi) between t It is created by the rain shadow of the Andes east of the desert. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... The Navy Prototype Optical Interferometer (NPOI) is an interferometer operated by the US Naval Observatory, the Naval Research Laboratory and The Lowell Observatory. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ... The CHARA Array is an astronomical optical interferometer operated by The Center for High Angular Resolution Astronomy (CHARA) at Georgia State University. ... 2005 is a common year starting on Saturday of the Gregorian calendar. ... The Overwhelmingly Large Telescope (OWL) is a conceptual design by the European Southern Observatory organization for a telescope which was intended to have a single aperture of 100 meters in diameter, but was later scaled down to a 60 meter diameter telescope. ... The Hale Telescope is the largest telescope at the Palomar Observatory. ... Palomar Observatory Palomar Mountain is a mountain in the Palomar Mountain Range in northern San Diego County, California, United States. ... It has been suggested that Kimax be merged into this article or section. ... // For the programming language, see Pyrex (programming language). ... The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California. ... The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California. ... Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. ... For other uses, see Galaxy (disambiguation). ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared with that of the Sun (left). ... St. ... Year 1919 (MCMXIX) was a common year starting on Wednesday (link will display the full calendar). ... The Leviathan of Parsonstown is a telescope located at Birr Castle. ... The castle. ... The Mount Wilson Observatory (MWO) is an astronomical observatory in Los Angeles County, California. ... 1897 photo of the 102 cm (40 inch) refractor at the Yerkes Observatory. ... Official language(s) None Capital Madison Largest city Milwaukee Area  Ranked 23rd  - Total 65,498 sq mi (169,790 km²)  - Width 260 miles (420 km)  - Length 310 miles (500 km)  - % water 17  - Latitude 42° 30′ N to 47° 05′ N  - Longitude 86° 46′ W to 92° 53′ W Population  Ranked... Year 1889 (MDCCCLXXXIX) was a common year starting on Tuesday (link will display the full calendar) of the Gregorian calendar (or a common year starting on Sunday of the 12-day slower Julian calendar). ... The Lick Observatory is an astronomical observatory, owned and operated by the University of California. ... For other uses, see San José. Nickname: Location of San Jose within Santa Clara County, California. ... The main cupola The 76-cm refractor at Nice Observatory The Nice Observatory (Observatoire de Nice) is located in Nice, France on the summit of Mont Gros. ... For the toll-free telephone number see Toll-free telephone number Year 1888 (MDCCCLXXXVIII) was a leap year starting on Sunday (click on link for calendar) of the Gregorian calendar (or a leap year starting on Friday of the 12-day slower Julian calendar). ... Despite the fact that the big refractor of the Paris Exposition Universelle 1900 was a financial failure for its sponsors there is not significant trace of a misfunction of the system, the photographic shots of the Lyra nebula taken inside the exhibition show it could be used inside the most... Anthem: Arrorró Capital Las Palmas de Gran Canaria and Santa Cruz de Tenerife Official language(s) Spanish Area  â€“ Total  â€“ % of Spain Ranked 13th  7,447 km²  1. ... The Swedish Solar Telescope (or SST) is a 1m telescope on La Palma in the Canary Islands. ... Aerial view of USNO. The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... Phobos (IPA: or [ˈfoÊŠ.bÉ™s]) (systematic designation: ) is the larger and closer of Mars two moons (the other being Deimos). ... Deimos (IPA or ; Greek Δείμος: Dread), is the smaller and outermost of Mars’ two moons, named after Deimos from Greek Mythology. ...

Other types

• Binoculars are just two monoculars mounted side-by-side with adjustments to let both be used. A major practical advantage of these telescopes is not magnification, so much as a brighter field of view at dusk and dawn. Monoculars and binoculars with built-in compasses are used by army artillery units and ships to navigate by triangulating from topographic (shore) features. Hand-held telescopes are limited by hand-shaking to about 7 power. The brightest-field, best-magnifying practical monocular is about 7x50.

Porro-prism binoculars with central focusing Binocular telescopes, or binoculars, (also known as field glasses) are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. ... Dusk in Breaux Bridge, Louisiana, USA. Dusk outside a plane on cruise. ... Dawn in Peng Chau, Hong Kong. ... This article is about the navigational instrument. ... Triangulation can be used to find the distance from the shore to the ship. ...

See also

• Astronomy
• Amateur telescope making
• Dipleidoscope
• List of optical telescopes
• Telescope

For other uses, see Astronomy (disambiguation). ... A 22 Newtonian reflector sits in front of the clubhouse at Stellafane, home of the Springfield Telescope Makers The field of amateur telescope making is considered an offshoot of the amateur astronomy community. ... There are very few or no other articles that link to this one. ... Several hundred more observatories (many optical) are listed here. ... This article does not cite any references or sources. ...

External links

• Basic Telescope Optics
• Online Telescope Math Calculator