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Encyclopedia > Dobsonian

In astronomy the Dobsonian is a type of alt-azimuth telescope mounting that became popular among amateur astronomers in the 1980s because of its extreme simplicity, low price, and rugged construction. The terms "Dobsonian" or "Dob" may also refer to any telescope that features this type of mount, although the telescopes themselves are typically of Newtonian design. Astrometry: the study of the position of objects in the sky and their changes of position. ... An Altazimuth or alt-azimuth mount is a simple mount used for moving a telescope or camera along two perpendicular axes of motion. ... In astronomy, the telescope mount is an important part of the overall design of an operational telescope. ... 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. ...

10" Newtonian telescope on Dobson mount
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10" Newtonian telescope on Dobson mount

Although its namesake, John Dobson, is frequently credited as having invented this mounting system in the 1950s, he does not make that claim. On the contrary, he points out that "for hundreds of years, wars were fought using cannon on 'Dobsonian' mounts." His innovation was in making large aperture telescopes affordable. ImageMetadata File history File links Download high resolution version (800x1067, 92 KB) Summary 10 Newton telescope on dobson mount Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... ImageMetadata File history File links Download high resolution version (800x1067, 92 KB) Summary 10 Newton telescope on dobson mount Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... 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. ... John Dobson in Wellington, New Zealand, April 2005 John L. Dobson (born September 14, 1915) is a highly influential amateur astronomer who has been dubbed the pied piper of astronomy and the star monk. He was the only amateur astronomer highlighted in the PBS series The Astronomers, and appeared twice... The word aperture means an opening, from the Latin aperire, to open. ...


Traditional mounting systems for large telescopes frequently cost more than the optical system they support. By grinding and polishing his own mirrors (frequently out of surplus porthole glass), and by constructing mounts out of little more than scrap building material, Dobson created what he called “sidewalk telescopes” for a fraction of the cost of commercial models. Scopes of this design tend to be very well balanced and have smooth operation, as well as being very compact, portable and easy to make. These features make the Dobsonian a favorite of amateur telescope makers. There is a strong tradition of amateur telescope making within the amateur astronomy community. ...

John Dobson admiring an example of the telescope mounting system that bears his name
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John Dobson admiring an example of the telescope mounting system that bears his name

The Dobsonian mount consists of three major parts. Azimuth (side-to-side) motion is provided by a turntable, on top of which sits a large box. Into the upper sides of the box are cut two semi-circular cutouts. Two disks are fixed to either side of the telescope tube at the balance point, and fit into the cutouts on the box to provide altitude (up-and-down) motion. The various bearing points are typically lined with teflon (although felt is also sometimes used) as a bearing surface. Image File history File links John Dobson (left), developer of the Dobsonian telescope mount. ... Image File history File links John Dobson (left), developer of the Dobsonian telescope mount. ... John Dobson in Wellington, New Zealand, April 2005 John L. Dobson (born September 14, 1915) is a highly influential amateur astronomer who has been dubbed the pied piper of astronomy and the star monk. He was the only amateur astronomer highlighted in the PBS series The Astronomers, and appeared twice... Azimuth is the horizontal component of a direction (compass direction), measured around the horizon toward the East, i. ... Altitude is the elevation of an object from a known level or datum, called zero level. ... Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910–1994) of DuPont in 1938 and introduced as a commercial product in 1946. ...


The entire mount is quite small in comparison to typical star-tracking systems, and can be easily transported. This has made it a favourite of amateur astronomers because it can be carried to star parties in the back of a small car and set up in moments. The result has been a fixation with ever-larger telescopes, which would otherwise require huge "traditional" mounts. Whereas a 8" Newtonian would be considered large 30 years ago, today 16" systems are common, and huge 32" systems not all that rare. Amateur astronomy, often called back yard astronomy, is a hobby whose participants enjoy observing celestial objects. ... A star party is a gathering of amateur astronomers for the purpose of observing the sky. ... 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. ...


Dobsonians do have a few limitations. Because they are not designed to track objects, users must nudge the scope every few minutes to compensate for the rotation of the Earth to keep an object in view. This makes them less suitable for astrophotography and CCD imaging. They also tend to lack computer controls and GPS systems, thus requiring users to find objects themselves. But, what they lack in modern conveniences, they make up for in economy. Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... Milky Way in Sagittarius. ... CCD can stand for: Charge-Coupled Device Confraternity of Christian Doctrine Carbonate Compensation Depth Council for a Community of Democracies MiniCD This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ...


John Dobson originally published instructions on how to make what came to be known as the Dobsonian telescope in his 1991 book How and Why to Make a User-Friendly Sidewalk Telescope (ISBN 0913399647), edited by Norman Sperling. The book treats the "why" as importantly as the "how", sharing Dobson's philosophy on the importance of popular access to astronomy for proper appreciation of the universe. Many other books and articles on the construction of Dobsonian telescopes have been published since. 1991 (MCMXCI) is a common year starting on Tuesday of the Gregorian calendar. ... Norman Sperling is an author, editor, publisher, teacher, and telescope designer living in San Mateo, California. ...


  Results from FactBites:
 
Dobsonian Telescope (724 words)
A Dobsonian is a reflecting telescope (uses a mirror, not a lens) in the same design as a Newtonian telescope (concave collecting mirror is at the rear of the telescope tube, eyepiece is on the side of tube, up near the front).
First, a Dobsonian is not computer controlled (a great expense anyway), so you need to figure out where to point it to see things.
By the way, some people construct their own Dobsonian mount, which is generally just as good as any commerical Dobsonian mount (picture at the top of the page is of someone's homemade Dob).
Dobsonian Telescopes - Shop Dobsonian.com (239 words)
Most of our dobsonian telescopes ship free, while the rest have incredibly low-cost shipping.
Our dobsonian telescopes are reliable, stylish and high-quality.
Dobsonian.com brings you the largest selection of dobsonian telescopes at prices that fit most any budget.
  More results at FactBites »

 
 

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