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With refractors of this type, the focal length meant a real physical length between the objective and the focus point. Reflecting telescopes can 'fold' their focal length by using mirrors, so they can have a physical length shorter than their optical focal length. Two important figures for telescopes
345:
The guide telescope for the 28-inch Grubb as of the 1890s was the
Corbett telescope with 6.5 inch aperture refractor. The 6.5 inch aperture Corbett telescope had also been used as a guide scope on the Lassell reflecting telescope in the 1880s. The 6.5 inch telescope was originally purchased used from
516:
An observer of Encke's in March 1918 had this to say of the comet on March 12, 1918, comparing to the early March 9, 1918 observation: "The comet much sharper, brighter, smaller; its diameter was 1 1/2', magnitude 77 (B.D. scale). Its magnitude in the 6-inch
Corbett was almost stellar, but in the 28
417:
The new dome was needed because the 28-inch Grubb was longer than the 12.8 inch aperture Merz. The Grubb has a focal length of 27 feet and 10 inches, while the old Merz had a focal length of 17 feet and 10 inches. The tower diameter is smaller than the length of the new Grubb telescope, so the dome
447:
The telescope is installed in the 'Great
Equatorial Building' at Greenwich. When it was installed at Herstmonceux, the 28-inch Grubb was installed in Dome F. The whole observatory was moved in the 1950s to a new installation at Herstmonceux in Sussex, however, astronomy was changing rapidly at the
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The 28-inch telescope was installed on the same mounting as an older 12.8 inch aperture refractor at the same location. The 12.8 inch was moved to be a guide telescope for the
Thompson 26-inch refractor. The mounting dates to the 1850s. The mounting is an English equatorial mount built by Ransomes
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The mounting was designed by George Airy in the 1850s, for the older 13-inch refractor, in conjunction with the firm
Ransomes and Simms. It is an equatorial design, that allows the telescope to rotate to compensate for the rotation of the Earth; this allows the telescope to stay fixed on certain
341:
The telescope is known as the largest aperture refractor in the United
Kingdom, and is a popular tourist attraction. The telescope now features in observing events in the 21st century. In the 1980s it was noted that there was an admission charge for visitors to look through the 28-inch.
226:
and the firm
Ransomes and Simms. The telescope is noted for its spherical dome which extends beyond the tower, nicknamed the "onion" dome. Another name for this telescope is "The Great Equatorial" which it shares with the building, which housed an older but smaller telescope previously.
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In 1987 a second staircase into the dome was added, to ease the flow of visitors in and out, the quantity of which was enough to make foot traffic on a single winding staircase difficult. The entrance door to the telescope is also noted for being made of iron, in the
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Originally it was rotated by a clockwork drive powered by water, and later in the 20th century this was replaced by electric motor driven system. In 1897 it was said that the clockwork water drive that "the water clock in general drives it with great precision."
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One reason for this was to have it ready for the tricentennial of
Greenwich Observatory in 1975. The telescope was recommissioned by Queen Elizabeth II in May 1975 after it was brought back from Herstmonceux. Since that time it has been under care of the
406:
The dome for the older, smaller telescope was taken down in 1892, and the new, larger dome for the 28-inch was finished by 1893. The older dome for the 12.8 inch refractor has been called a 'drum dome' whereas the 28-inch is called the 'onion dome'.
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In the early 21st century the telescope was normally free to visit, and could reached by going through a gift shop at the observatory when the facilities were open. However, it was also featured in an edutainment presentation called
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in 1947, and operated there between 1957-1970, but was moved back to
Greenwich in 1971. The return of the 28-inch refractor in 1971 to the Greenwich Observatory site was featured in an episode of the British television show
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point in the heavens. The telescope tube is mounted in a latticework of iron, that is mounted on each end on spindle that rest on a stone and metal pier.
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and that experience cost the price of few pounds' currency. In the presentation there was multimedia and questions could be asked of a presenter.
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Between 1960 and 1963 over 1300 observations of 233 double stars were conducted with the filar micrometer from
Herstmonceux with the 28 inch.
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A 28-inch aperture refractor was ordered from the telescope maker Grubb in 1885. It was installed by 1893 in the Great Equatorial building.
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to be an astronomical observer on March 4, 1675; by the summer of 1676 Flamsteed operated from the new Flamsteed House on Greenwich hill.
297:
The dome's overall design dates to 1892 but the current dome is made of fibreglass and dates to 1971, after the original made of iron and
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The dome for the 28-inch is noted for being called the "onion dome" and the original manufacture from 1893 was made of an iron grid and
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An 1897 report on the telescope remarked, "The 28-inch Refractor has been in use throughout the year and is quite satisfactory."
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1077:"Results of Micrometer Measures of Double Stars made with 28-inch Refractor at the Royal Observatory, Greenwich, the year 1912"
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An example of observations taken with the 28-inch was a survey of stars in 1912, measured with a bifilar position micrometer.
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orbits the Sun about every 3.3 years, so in addition to 1918, it also approached the Sun in 1913-4 and again in 1921-22.
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Illustration of the older telescope; the 28-inch used the same mount. However, it needed a new dome due to being longer
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Astronomical and Magnetical and Meteorological Observations Made at the Royal Observatory, Greenwich, in the Year ...
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Astronomical and Magnetical and Meteorological Observations Made at the Royal Observatory, Greenwich, in the Year ...
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242:. It was placed in the renovated original dome at Greenwich for the tricentennial celebration of the observatory.
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glass. The mounting is older however and dates to the 1850s, having been designed by Royal Observatory director
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1122:"Observations of Encke's Comet (1917 c.) made with the 28-inch Equatorial at the Royal Observatory, Greenwich"
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Observations Made at the Royal Observatory, Greenwich in the Year ... in Astronomy, Magnetism and Meteorology
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time with a major focus on observatory location; astronomers could review data from instruments elsewhere.
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931:"The Royal Observatory Greenwich - where east meets west: Telescope: The Lassell 2-foot Reflector (1847)"
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was removed during the Second World War for safekeeping, and then put back after that conflict was over.
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In the 1890s the telescope was used to take measurements of various stars, the diameter of the planet
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Star Ware: The Amateur Astronomer's Guide to Choosing, Buying, and Using Telescopes and Accessories
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837:"The Royal Observatory Greenwich - where east meets west: Telescope: 28-inch Refractor (1893)"
807:"The Royal Observatory Greenwich - where east meets west: Telescope: 28-inch Refractor (1893)"
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In the early 1900s the 28-inch was used to measure the diameter of the planet Jupiter using a
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a Mr Corbett, and was on a mobile tripod; it was acquired as an expedition telescope for the
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640:
Wright, D. C. (1990). "The 28-inch Refractor at Greenwich - a History of Two Telescopes".
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was in need of refurbishment when the telescope was moved back to Greenwich in the 1970s.
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956:"The Royal Observatory Greenwich - where east meets west: Telescope: Corbett Equatorial"
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The telescope is reported to have a resolving power of 0.16 arcseconds. The telescope's
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491:. The fifth satellite of Jupiter was just discovered in 1892, and was later named
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are the aperture and focal length, which affect the equations that describe their
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In the 1890s the mount was able to accommodate the 28-inch, and was thus re-used.
708:"28-inch telescope : Scenic attractions : Visit the museum : NMM"
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The lower end of the equatorial framework that the telescope tube is held in
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When the telescope was moved back to Greenwich in 1971, a new dome made of
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1062:
A Brief Account of the Lick Observatory of the University of California
483:, the 5th satellite of Jupiter, and various measurements of the planet
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200:, where it was first installed in 1893. It is a 28-inch ( 71 cm)
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402:
Dome of the Royal Observatory Greenwich 28-inch refractor, circa 1900
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986:"How to Plan an Astronomy Trip to the Royal Greenwich Observatory"
861:
Hilton, Wallace A. (1978). "Tricentennial Greenwich Observatory".
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strike during the Second World War, and was taken down in 1953.
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1182:. NASA, Office of Scientific and Technical Information. 1965.
495:(so at that time there were only 5 moons known including the
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List of largest optical telescopes in the British Isles
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The observatory is popular for tourism in modern times.
773:
Wright, D. C. (1990). "1990QJRAS..31..551W Page 551".
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List of largest optical telescopes in the 19th century
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The observer's end of the telescope, showing various
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Royal Observatory Former Great Equatorial Building,
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Quarterly Journal of the Royal Astronomical Society
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Quarterly Journal of the Royal Astronomical Society
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1126:Monthly Notices of the Royal Astronomical Society
1081:Monthly Notices of the Royal Astronomical Society
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505:In March 1918 the 28 inch took observations of
444:in the style of the older dome was installed.
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584:List of largest optical refracting telescopes
563:The dome ceiling and the top of the telescope
41:The dome of Greenwich 28-inch Great refractor
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418:had to be bigger to accommodate its length.
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517:inch no definitive nucleus could be seen."
234:in May 1975 after it was brought back from
218:. The achromatic lens was made Grubb from
1179:Scientific and Technical Aerospace Reports
410:The original 1893 dome was made by Messrs
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1011:Harrington, Philip S. (16 October 2002).
1197:28-inch visual (refractor) telescope RMG
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157:Location of Greenwich 28-inch refractor
1166:J. Barker and sold by J. Murray. 1908.
1048:J. Barker and sold by J. Murray. 1897.
683:"28-inch visual (refractor) telescope"
524:, and also a double-image micrometer.
479:, measurements of the location of the
214:, and was made by the telescope maker
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1202:Telescope: 28-inch Refractor (1893)
1065:. The University Press. p. 7–.
712:webarchive.nationalarchives.gov.uk
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960:www.royalobservatorygreenwich.org
935:www.royalobservatorygreenwich.org
841:www.royalobservatorygreenwich.org
811:www.royalobservatorygreenwich.org
543:Closeup of lower end of telescope
1087:(2): 137–154. 12 December 1913.
210:telescope, otherwise known as a
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896:Slade, Margot (5 August 1984).
755:. H.M. Stationery Office. 1904.
121:
433:. This dome was damaged in a
394:The Great Refractor dome, 2013
1:
1132:(6): 448–449. 12 April 1918.
898:"A Century at Zero Longitude"
294:and Sims, and Williams Sims.
1222:Royal Observatory, Greenwich
270:The observatory sits amidst
198:Royal Observatory, Greenwich
553:Fisheye panorma of interior
424:properties of magnification
194:Greenwich 28-inch refractor
30:Greenwich 28-inch refractor
18:Greenwich 28 inch refractor
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652:Royal Astronomical Society
356:Great Equatorial Encounter
126:28 in (0.71 m)
52:Royal Borough of Greenwich
1059:Lick Observatory (1894).
1017:. John Wiley & Sons.
311:The 28-inch was moved to
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328:National Maritime Museum
174:Related media on Commons
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1094:10.1093/mnras/74.2.137
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105:Telescope style
990:Space Tourism Guide
875:1978PhTea..16...95H
863:The Physics Teacher
787:1990QJRAS..31..551W
718:on 14 November 2008
660:1990QJRAS..31..551W
274:in London, England.
84:51.4777°N 0.00117°W
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716:the original
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580:(Since 1838)
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460:Observations
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996:14 November
654:: 551–566.
224:George Airy
87: /
63:Coordinates
47:Location(s)
1211:Categories
965:31 October
940:26 October
915:25 October
846:25 October
816:26 October
791:(Page 560)
722:25 October
600:References
442:fibreglass
72:51°28′40″N
1148:0035-8711
1103:0035-8711
910:0362-4331
869:(2): 95.
454:Victorian
284:eyepieces
212:refractor
205:objective
75:0°00′04″W
572:See also
531:Interior
493:Amalthea
362:Mounting
202:aperture
123:Diameter
871:Bibcode
783:Bibcode
656:Bibcode
477:Jupiter
456:style.
246:History
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1021:
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485:Saturn
240:Sussex
167:
111:
650:(4).
386:Domes
181:[
1144:ISSN
1099:ISSN
1019:ISBN
998:2019
967:2019
942:2019
917:2019
906:ISSN
848:2019
818:2019
724:2019
487:and
208:lens
192:The
1134:doi
1089:doi
879:doi
499:).
238:in
1213::
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1130:78
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1111:^
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