Refractors are criticized for their relatively high-degree of residual chromatic and spherical aberration. This affects shorter focal lengths more than longer ones. A 4" F6 achromatic refractor is likely to show considerable color fringing. (generally a purple halo around bright objects) A 4" F16 will have little color fringing. In very large apertures, there is also a problem of lens sagging, a result of gravity deforming glass. There is a further problem of glass defects, striae or small air bubbles trapped within the glass. In addi ...

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Refracting telescope, Refracting telescope - Technical difficulties, Refracting telescope - Notable refracting telescopes

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Lick Observatory was the world's first mountain-top observatory. The observatory was constructed between 1876 and 1887, from a bequest from James Lick. In 1887 Lick's body was buried under the future site of the telescope, with a brass tablet bearing the inscription, "Here lies the body of James Lick." Before construction could begin, a road to the site had to be built. All of the construction materials had to be brought to the site by horse and mule-drawn wagons, which could not negotiate a steep grade. To keep the grade below ...

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Lick Observatory, Lick Observatory - Early history, Lick Observatory - Significant discoveries, Lick Observatory - Equipment, Lick Observatory - External link

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Refractors are criticized for their relatively high-degree of residual chromatic and spherical aberration. In very large apertures, there is also a problem of lens sagging, a result of gravity deforming glass. There is a further problem of glass defects, striae or small air bubbles trapped within the glass. In addition, glass is opaque to certain wavelengths, and even visible light is dimmed by reflection and absorption when it crosses the air-glass interfaces and passes through the glass itself. Most -or all- these problems are avoided by using r ...

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Refracting telescope, Refracting telescope - Technical difficulties, Refracting telescope - Notable refracting telescopes

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The Yerkes Observatory is an astronomy observatory of the University of Chicago, in Williams Bay, Wisconsin. It was created in 1897 by George Ellery Hale and financed by Charles T. Yerkes. The observatory represented a shift in the thinking of observatories, from mere housing for a telescope and observer, to the modern concept of observation equipment integrated with laboratory space for physics and chemistry. A 102 cm (40 inch) refracting telescope built by the master optician Alvin Clark is located inside; it was the largest telescope until the construction of Mount Wilson's reflecto ...

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A telescope (from the Greek tele = 'far' and skopein = 'to look or see'; teleskopos = 'far-seeing') is an optical tool which gathers and focuses electromagnetic radiation. Telescopes increase the apparent angular size of distant objects, as well as their apparent brightness. Telescopes are used for astronomy and in many non-astronomical instruments including theodolites, transits, spotting scopes, monoculars, binoculars, camera lenses and spyglasses. The word "telescope" usually refers to optical telescopes, but there are telescopes for mo ...

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• Telescope - Types
• Telescope - Telescope mountings
• Telescope - Research telescopes
• Telescope - Imperfect images
• Telescope - The five Seidel aberrations
• Telescope - The chromatic aberrations
• Telescope - Famous optical telescopes
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The 50 cm refractor at Nice Observatory. 20 inch refractor at the Observatories at Chabot Space and Science Center in Oakland, California. 8 inch refractor at the Observatories at Chabot Space and Science Center in Oakland, California. ...

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Refracting telescope, Refracting telescope - Technical difficulties, Refracting telescope - Notable refracting telescopes

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The first telescopes may have been Assyrian crystal lenses. Article The Visby lenses tentatively suggest that the technology was known to the Arabs and Persians then to the Vikings in the 10th century. Leonard Digges is sometimes credited with the invention in England in the 1570s, but usually credit for assembling the first telescope is usually given to an unknown Dutch spectacle maker in about 1608. Some name that person as Hans Lippershey (c1570-c1619), but Jacob Metius and Zacharias Jansen also claimed to have invented a telescope ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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List of reference tables - Standards. List of standards topics (these could easily be cross-referenced under other relevant categories as well) International Standards List of ISO standards ISO 639 language names ISO 3166 country codes Time zones List of country calling codes List of Internet TLDs List of plastic recycling codes United States Standards Federal Standard 1037C (Glossary of telecommunication t ...

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The first telescopes may have been Assyrian crystal lenses. Article Though the Visby lenses tentatively suggest that the technology was known to the Arabs and then to the Vikings in the 10th century, credit for assembling the first telescope is usually given to an unknown Dutch spectacle maker in about 1608. Some name that person as Hans Lippershey (c1570-c1619). 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 ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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List of reference tables - Cities. List of city listings by country List of cities that have been the birthplace of a genre of music Capitals List of national capitals by name (present and past) List of capitals and larger cities by country List of capitals of subnational entities List of current and former capital cities within U.S. states List of metropolitan areas by population List of the world's most populous citiesSee also:

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List of reference tables - Business finance and economics. List of accounting topics List of management topics List of marketing topics List of economics topics List of economic geography topics List of employee-owned companies List of finance topics List of human resource management topics List of information technology management topics List of international trade topics List of business law topics List of p ...

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List of reference tables - Agriculture and food. List of cocktails List of commercial brands of beer List of diets List of Fast-food restaurant chains List of food additives List of foods named after people List of food topics List of French cheeses List of grape varieties List of recipes List of restaurant ...

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Telescopes are broadly classified into two main types. Optical telescopes Radio telescopes Optical telescopes are also divided into two types. Galilean refracting telescopes Newtonian reflecting telescopes Galilean or refracting telescopes employ the refractive properties of light, and are constructed of lenses. These can be used for both terrestrial and astronomical viewing. Newtonian or reflecting telescopes employ the reflect ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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Most large research telescopes can operate as either a cassegrain telescope (longer focal length, and a narrower field with higher magnification) or newtonian telescope (brighter field). They have a pierced primary, a newtonian focus, and a spider to mount a variety of replaceable secondaries. A new era of telescope making was inaugurated by the MMT, with a mirror composed of six segments synthesizing a mirror of 4.5 metres diameter (this has now been replaced by a single 6.5m mirror). Its example was followed by ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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A simple telescope mount is an altitude-azimuth or altazimuth mount. It is similar to that of a surveying transit. A fork rotates in azimuth (in the horizontal plane), and bearings on the tips of the fork allow the telescope to vary in altitude (in a vertical plane). A dobsonian mount is a type of altazimuth mount which has proven to be very popular as it is simple and cheap to make. The major problem with using an altazimuth for astronomy is that both axes must be continuously adjusted to compensate for the Earth ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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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 common ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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The telescopes are broadly classified into two main categories. Optical telescopes Radio telescopes The optical telescopes are again divided into two Galilean refracting telescopes Newtonian reflecting telescopes The Galilean or refracting telescopes used refraction property of light. They were made up of lenses. They can be used for both terrestrial as well as astronomical viewing. The Newtonian or reflecting telescopes used reflec ...

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Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

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A simple telescope mount is an altitude-azimuth or altazimuth mount. It is similar to that of a surveying transit. A fork rotates in azimuth (in the horizontal plane), and bearings on the tips of the fork allow the telescope to vary in altitude (in a vertical plane). A Dobsonian mount is a type of altazimuth mount which has proven to be very popular as it is simple and inexpensive. When using an altazimuth for astronomy, both axes must be continuously adjusted to compensate for the Earth's rotation. Even if this i ...

See also:

Telescope, Telescope - History, Telescope - Types, Telescope - Telescope mountings, Telescope - Research telescopes, Telescope - Imperfect images, Telescope - The five Seidel aberrations, Telescope - The chromatic aberrations, Telescope - Famous optical telescopes, Telescope - Related lists

Read more here: » Telescope: Encyclopedia II - Telescope - Telescope mountings