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

Read more here: » Refracting telescope: Encyclopedia II - Refracting telescope - Notable refracting telescopes

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History of telescopes, History of telescopes - Refracting telescopes, History of telescopes - Reflecting telescopes, History of telescopes - Achromatic Telescope, History of telescopes - Related links

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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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• Yerkes Observatory - Related topics

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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 ...

Including:

• 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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Alvan Graham Clark (July 10, 1832 – June 9, 1897), born in Fall River, Massachusetts, was an American astronomer and telescope-maker. He was the son of Alvan Clark. In 1862, while testing a new 18-inch refracting telescope he discovered Sirius B, the magnitude 8 companion of Sirius. Alvan Graham Clark - Reference. http://reference.allrefer.com/encyclopedia/C/Clark-Al.html ...

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• Alvan Graham Clark - Reference

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Adaptive optics is a technology to improve the performance of (usually) astronomical telescopes by reducing the effects of atmospheric distortion, or astronomical seeing. Adaptive optics works by measuring the distortion and rapidly compensating for it either using deformable mirrors or material with variable refractive properties. While the technique was theoretically understood for some time, it was only advances in computer technology during the 1990s that finally made the technique practical. Adaptive optics should not be confused ...

Including:

• Adaptive optics - Introduction
• Adaptive optics - Uses of adaptive optics
• Adaptive optics - Beam stabilization

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Anti-reflective or antireflection (AR) coatings are a type of optical coating applied to lenses and other devices to reduce reflection from optical surfaces. This often improves the efficiency of the system; this is especially important if the light wasted by reflections is difficult to obtain, i.e. from a large telescope, an obstacle on a dark roadway, or an intricate optics experiment. They also have qualitative benefits like making the eyes of a glasses-wea ...

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Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by the Earth's atmosphere. The astronomical seeing conditions on a given night at a given location describe how much the Earth's atmosphere perturbs the images of stars as seen through a telescope. The most common seeing measurement is the diameter (technically Full Width Half Maximum) of the seeing disc. The seeing disc diameter ("seeing") is a reference to the best possible angular resolution which can be achiev ...

Including:

• Astronomical seeing - The Effects of Astronomical Seeing
• Astronomical seeing - Measures of Astronomical Seeing
• Astronomical seeing - The FWHM of the seeing disc
• Astronomical seeing - r0 and t0
• Astronomical seeing - The CN2 profile
• Astronomical seeing - Overcoming Atmospheric Seeing

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There is a strong tradition of amateur telescope making within the amateur astronomy community. The classic amateur telescope is the Newtonian reflector with a dobsonian type mount, also known as a "Dobsonian telescope." Some also build refractors and a very few attempt compound designs such as the Maksutov telescope. Amateur telescope makers typically make the most critical parts of ...

Including:

• Amateur telescope making - Telescope design
• Amateur telescope making - Mirror making
• Amateur telescope making - Grinding
• Amateur telescope making - Polishing
• Amateur telescope making - Mirror testing
• Amateur telescope making - Figuring the mirror
• Amateur telescope making - Aluminizing or silvering the mirror
• Amateur telescope making - Telescope construction
• Amateur telescope making - Tube
• Amateur telescope making - Mount
• Amateur telescope making - Telescope making books and other published information

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Angular resolution describes the resolving power of a telescope. Angular resolution - Definition of terms. Resolving power is the ability of a microscope or telescope to measure the angular separation of images that are close together. Resolution is the minimum distance between distinguishable objects, in microscopy. These terms also apply to other angle and position measuring devices. Resolution, more generally, is the precision of any instrument to measure a continuous variable ...

Including:

• Angular resolution - Definition of terms
• Angular resolution - Explanation
• Angular resolution - Telescope case
• Angular resolution - Microscope case

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Borosilicate glass is a particular type of glass, better known under the brand names Pyrex and Kimax. It was first developed by German glassmaker Otto Schott in the late 19th century and sold under the brand name "Duran" in 1893. After Corning Glass Works developed Pyrex in 1924, it became a synonym for borosilicate glass in the English-speaking world. In addition to the quartz, sodium carbonate, and calcium carbonate traditionally used in glassmaking, boron is used in the manufacture of borosilicate glass. Typically, the resul ...

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• Borosilicate glass - External link

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Sir David Brewster, (December 11, 1781 – February 10, 1868) was a Scottish scientist and writer. He was born at Jedburgh, where his father, a teacher of high reputation, was rector of the grammar school. At the age of twelve he was sent to the University of Edinburgh, being intended for the clergy. However, he had already shown a strong inclination for natural science, and this had been fostered by his intimacy with a "self-taught philosopher, astronomer and mathematician," as Sir Walter Scott called him, of great local fame—James Veitch of Inchbonn ...

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Binocular telescopes or binoculars are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, one to be viewed through each of the user's eyes. By contrast, relatively small single-tube telescopes are often called "monoculars". The advantages of a binocular over a monocular telescope are: it gives a 3-dimensional image with depth: the two distinct views presented from slightly different viewpoints to each of the viewer's eyes merge to produc ...

Including:

• Binoculars - Prismatic binoculars
• Binoculars - Design details
• Binoculars - Optical parameters
• Binoculars - Optical construction
• Binoculars - Image stabilisation
• Binoculars - Maintenance
• Binoculars - Choosing binoculars

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Aberration in optical systems (lenses, prisms, mirrors or series of them intended to produce a sharp image) generally leads to blurring of the image. It occurs when light from one point of an object after transmission through the system arrives in different points. Instrument-makers need to correct optical systems to compensate for aberration. The articles reflection, refraction and caustic discuss the general features of reflected and refracted rays. Aberrations fall into two classes: chromatic aberrations ...

Including:

• Aberration in optical systems - Monochromatic aberration
• Aberration in optical systems - Aberration of axial points spherical aberration in the restricted sense
• Aberration in optical systems - Aberration of elements i.e. smallest objects at right angles to the axis
• Aberration in optical systems - Aberration of lateral object points points beyond the axis with narrow pencils. Astigmatism.
• Aberration in optical systems - Aberration of lateral object points with broad pencils. Coma.
• Aberration in optical systems - Curvature of the field of the image
• Aberration in optical systems - Distortion of the image
• Aberration in optical systems - Analytic treatment of aberrations
• Aberration in optical systems - Practical elimination of aberrations
• Aberration in optical systems - Chromatic or colour aberration
• Aberration in optical systems - Authorities.

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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

Read more here: » Refracting telescope: Encyclopedia II - Refracting telescope - Technical difficulties

A refracting telescope is an instrument that is constituted of one or several lenses and that focuses the luminous rays toward one point called focus. The role of the eyepiece situated after the focus is to shape the picture so that it is visible for the eyes as well as to enlarge this one. A good refracting telescope is an instrument that one retains all his or her life, even after the acquisition of a bigger telescope. The refracting telescope, by its reduced opening (therefore little luminous), is especially adapted to the observat ...

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Skygazing, Skygazing - Naked eye skygazing, Skygazing - Diurnal observation, Skygazing - Nocturnal observation, Skygazing - Binocular gazing, Skygazing - Choice of binoculars, Skygazing - Advice on observational techniques, Skygazing - Observations with a refracting telescope, Skygazing - Choice of the refracting telescope, Skygazing - Advice of usage, Skygazing - The observation with a reflecting telescope, Skygazing - Types of reflecting telescope

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The historical sequence of events now brings us to the discovery of the achromatic telescope. The first person who succeeded in making achromatic refracting telescopes seems to have been Chester Moor Hall, a gentleman of Essex. He argued that the different humours of the human eye so refract rays of light as to produce an image on the retina which is free from colour, and he reasonably argued that it might be possible to produce a like result by combining lenses composed of different refracting media. After devoting some time to the i ...

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History of telescopes, History of telescopes - Refracting telescopes, History of telescopes - Reflecting telescopes, History of telescopes - Achromatic Telescope, History of telescopes - Related links

Read more here: » History of telescopes: Encyclopedia II - History of telescopes - Achromatic Telescope

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

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

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

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