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Hale Telescope

Coordinates:33°21′23″N116°51′54″W/ 33.35628°N 116.86489°W/33.35628; -116.86489
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For the smaller Hale Telescope at Mount Wilson, see60-inch Hale Telescope
Hale Telescope
Alternative namespalomarEdit this at Wikidata
Named afterGeorge Ellery HaleEdit this on Wikidata
Part ofPalomar ObservatoryEdit this on Wikidata
Location(s)Palomar Mountain, California,US
Coordinates33°21′23″N116°51′54″W/ 33.35628°N 116.86489°W/33.35628; -116.86489Edit this at Wikidata
Altitude1,713 m (5,620 ft)Edit this at Wikidata
First lightJanuary 26, 1949, 10:06pmPST
DiscoveredCaliban,Sycorax,Jupiter LI,Alcor B
Telescope styleoptical telescope
reflecting telescopeEdit this on Wikidata
Diameter200 in (5.1 m)Edit this at Wikidata
Collecting area31,000 sq in (20 m2)Edit this at Wikidata
Focal length16.76 m (55 ft 0 in)Edit this at Wikidata
Mountingequatorial mountEdit this on Wikidata
Websitewww.astro.caltech.edu/palomar/about/telescopes/hale.htmlEdit this at Wikidata
Hale Telescope is located in the United States
Hale Telescope
Location of Hale Telescope
Related media on Commons
[edit on Wikidata]

TheHale Telescopeis a 200-inch (5.1 m),f/3.3reflecting telescopeat thePalomar ObservatoryinSan Diego County,California,US, named after astronomerGeorge Ellery Hale.With funding from theRockefeller Foundationin 1928, he orchestrated the planning, design, and construction of the observatory, but with the project ending up taking 20 years he did not live to see its commissioning. The Hale was groundbreaking for its time, with double the diameter of the second-largesttelescope,and pioneered many new technologies intelescope mountdesign and in the design and fabrication of its large aluminum coated "honeycomb" lowthermal expansionPyrexmirror.[1]It was completed in 1949 and is still in active use.

The Hale Telescope represented the technological limit in building large optical telescopes for over 30 years. It was thelargest telescope in the worldfrom its construction in 1949 until theSovietBTA-6was built in 1976, and the second largest until the construction of theKeck ObservatoryKeck 1 inHawaiiin 1993.

History[edit]

Base of the tube
Crab Nebula, 1959

Hale supervised the building of the telescopes at theMount Wilson Observatorywith grants from theCarnegie Institution of Washington:the 60-inch (1.5 m) telescope in 1908 and the 100-inch (2.5 m) telescope in 1917. These telescopes were very successful, leading to the rapid advance in understanding of the scale of theUniversethrough the 1920s, and demonstrating to visionaries like Hale the need for even larger collectors.[citation needed]

The chief optical designer for Hale's previous 100-inch telescope wasGeorge Willis Ritchey,who intended the new telescope to be ofRitchey–Chrétiendesign. Compared to the usual parabolic primary, this design would have provided sharper images over a larger usable field of view. However, Ritchey and Hale had a falling-out. With the project already late and over budget, Hale refused to adopt the new design, with its complex curvatures, and Ritchey left the project. The Mount Palomar Hale Telescope turned out to be the last world-leading telescope to have a parabolicprimary mirror.[2]

In 1928 Hale secured a grant of $6 million from theRockefeller Foundationfor "the construction of an observatory, including a 200-inch reflecting telescope" to be administered by theCalifornia Institute of Technology(Caltech), of which Hale was a founding member. In the early 1930s, Hale selected a site at 1,700 m (5,600 ft) onPalomar MountaininSan Diego County, California,US, as the best site, and less likely to be affected by the growing light pollution problem in urban centers likeLos Angeles.TheCorning Glass Workswas assigned the task of making a 200-inch (5.1 m) primary mirror. Construction of the observatory facilities and dome started in 1936, but because of interruptions caused byWorld War II,the telescope was not completed until 1948 when it was dedicated.[3]Due to slight distortions of images, corrections were made to the telescope throughout 1949. It became available for research in 1950.[3]

Postage Stamp. The US Post Office issued a 3c postage stamp in 1948 commemorating the Hale Telescope and Observatory.

A functioning one-tenth scale model of the telescope was also made at Corning.[4]

The 200-inch (510 cm) telescope sawfirst lighton January 26, 1949, at 10:06pmPST[5][6]under the direction of American astronomerEdwin Powell Hubble,targetingNGC 2261,an object also known as Hubble's Variable Nebula.[7][8]

The telescope continues to be used every clear night for scientific research by astronomers from Caltech and their operating partners,Cornell University,theUniversity of California,and theJet Propulsion Laboratory.It is equipped with modern optical and infrared array imagers, spectrographs, and anadaptive optics[9]system. It has also usedlucky camimaging, which in combination with adaptive optics pushed the mirror close to itstheoretical resolutionfor certain types of viewing.[9]

One of the Corning Labs' glass test blanks for the Hale was used for theC. Donald Shane telescope's 120-inch (300 cm) primary mirror.[10]

The collecting area of the mirror is about 31,000 square inches (20 square meters).[11]

Components[edit]

Mounting structures[edit]

The Hale Telescope uses a special type ofequatorial mountcalled a "horseshoe mount", a modified yoke mount that replaces the polar bearing with an open "horseshoe" structure that gives the telescope full access to the entire sky, includingPolarisand stars near it. The optical tube assembly (OTA) uses aSerrurier truss,then newly invented byMark U. Serrurierof Caltech in Pasadena in 1935, designed to flex in such a way as to keep all of the optics in alignment.[12]

Left:The 200-inch (508 cm) Hale Telescope inside on itsequatorial mount.
Right:Principle of operation of aSerrurier trusssimilar to that of the Hale Telescope compared to a simple truss. For clarity, only the top and bottomstructural elementsare shown. Red and green lines denote elements undertensionandcompression,respectively.

200-inch mirror[edit]

The 5 meter (16 ft. 8 in.) mirror in December 1945 at the Caltech Optical Shop when grinding resumed following World War 2. The honeycomb support structure on the back of the mirror is visible through the surface.

Originally, the Hale Telescope was going to use a primary mirror of fused quartz manufactured by General Electric,[13]but instead the primary mirror was cast in 1934 atCorning Glass Worksin New York state using Corning's then new material calledPyrex(borosilicate glass).[14]

Entrance door to 200 inch Hale telescope dome

The mirror was cast in a mold with 36 raised mold blocks (similar in shape to awaffle iron). This created ahoneycomb mirrorthat cut the amount of Pyrex needed down from over 40 short tons (36 t) to just 20 short tons (18 t), making a mirror that would cool faster in use and have multiple "mounting points" on the back to evenly distribute its weight (note – see external links 1934 article for drawings).[15]The shape of a central hole was also part of the mold so light could pass through the finished mirror when it was used in aCassegrainconfiguration (a Pyrex plug for this hole was also made to be used during the grinding and polishing process[16]). While the glass was being poured into the mold during the first attempt to cast the 200-inch mirror, the intense heat caused several of the molding blocks to break loose and float to the top, ruining the mirror. The defective mirror was used to test the annealing process. After the mold was re-engineered, a second mirror was successfully cast.[citation needed]

After cooling several months, the finished mirror blank was transported by rail to Pasadena, California.[17][18]Once in Pasadena the mirror was transferred from the rail flat car to a specially designed semi-trailer for road transport to where it would be polished.[19]In the optical shop in Pasadena (now the Synchrotron building at Caltech) standard telescopemirror makingtechniques were used to turn the flat blank into a precise concave parabolic shape, although they had to be executed on a grand scale. A special 240 in (6.1 m) 25,000 lb (11 t)mirror celljig was constructed which could employ five different motions when the mirror was ground and polished.[20]Over 13 years almost 10,000 lb (4.5 t) of glass was ground and polished away, reducing the weight of the mirror to 14.5 short tons (13.2 t). The mirror was coated (and still is re-coated every 18–24 months) with a reflective aluminum surface using the same aluminum vacuum-deposition process invented in 1930 by Caltech physicist and astronomerJohn Strong.[21]

The Hale's 200 in (510 cm) mirror was near the technological limit of a primary mirror made of a single rigid piece of glass.[22][23]Using a monolithic mirror much larger than the 5-meter Hale or 6-meter BTA-6 is prohibitively expensive due to the cost of both the mirror, and the massive structure needed to support it. A mirror beyond that size would also sag slightly under its own weight as the telescope is rotated to different positions,[24][25]changing the precision shape of the surface, which must be accurate to within 2 millionths of an inch (50nm). Modern telescopes over 9 meters use a different mirror design to solve this problem, with either a single thin flexible mirror or a cluster of smallersegmented mirrors,whose shape is continuously adjusted by a computer-controlledactive opticssystem using actuators built into themirror support cell.[citation needed]

Dome[edit]

The moving weight of the upper dome is about 1000 US tons, and can rotate on wheels.[26]The dome doors weigh 125 tons each.[27]The dome is made of welded steel plates about 10 mm thick.[26]

Observations and research[edit]

Dome of the 200-inch aperture Hale Telescope

The first observation of the Hale Telescope was ofNGC 2261on January 26, 1949.[28]

During its first 50 years, the Hale Telescope made many significant contributions to stellar evolution, cosmology, and high-energy astrophysics.[29]Similarly, the telescope, and the technology developed for it, advanced the study of the spectra of stars, interstellar matter, AGNs, and quasars.[30]

Quasarswere first identified as high redshift sources by spectra taken with the Hale Telescope.[31]

Halley's Comet(1P) upcoming 1986 approach to the Sun was first detected by astronomersDavid C. Jewittand G. Edward Danielson on 16 October 1982 using the 200-inch Hale Telescope equipped with aCCD camera.[32]

Two moons of the planetUranuswere discovered in September 1997, bringing the planet's total known moons to 17 at that time.[33]One wasCaliban(S/1997 U 1), which was discovered on 6 September 1997 byBrett J. Gladman,Philip D. Nicholson,Joseph A. Burns,andJohn J. Kavelaarsusing the 200-inch Hale Telescope.[34]The other Uranian moon discovered then isSycorax(initial designation S/1997 U 2) and was also discovered using the 200 inch Hale Telescope.[35]

TheCornell Mid-Infrared Asteroid Spectroscopy(MIDAS) survey used the Hale Telescope with a spectrograph to study spectra from 29 asteroids.[36]

In 2009, using a coronograph, the Hale Telescope was used to discover the starAlcor B,which is a companion to Alcor in theBig Dipper.[37]

In 2010, a new satellite of planetJupiterwas discovered with the 200-inch Hale, called S/2010 J 1 and later namedJupiter LI.[38]

In October 2017 the Hale Telescope was able to record the spectrum of the first recognized interstellar object,1I/2017 U1( "ʻOumuamua" ); while no specific mineral was identified it showed the visitor had a reddish surface color.[39][40]

In December 2023 the Hale Telescope began serving as the receiving antenna for theDeep Space Optical Communicationsexperiment on NASA'sPsyche mission.[41]

Direct imaging of exoplanets[edit]

Up until the year 2010,telescopescould onlydirectly imageexoplanets under exceptional circumstances. Specifically, it is easier to obtain images when the planet is especially large (considerably larger thanJupiter), widely separated from its parent star, and hot so that it emits intense infrared radiation. However, in 2010 a team fromNASA'sJet Propulsion Laboratorydemonstrated that avortex coronagraphcould enable small scopes to directly image planets.[42]

Direct image ofexoplanetsaround the starHR8799using avortex coronagraphon a 1.5m portion of the Hale Telescope

Comparison[edit]

Size comparison of the Hale Telescope (upper left, blue) to some modern and upcomingextremely large telescopes

The Hale had four times the light-collecting area of the second-largest scope when it was commissioned in 1949. Other contemporary telescopes were theHooker Telescopeat the Mount Wilson Observatory and theOtto Struve Telescopeat the McDonald Observatory.[citation needed]

The three largest telescopes in 1949
# Name /
Observatory 		Image Aperture Altitude First
Light 		Special advocate(s)
1 Hale Telescope
Palomar Obs. 		200-inch
508 cm 		1713 m
(5620 ft) 		1949 George Ellery Hale
John D. Rockefeller
Edwin Hubble
2 Hooker Telescope[43]
Mount Wilson Obs. 		100-inch
254 cm 		1742 m
(5715 ft) 		1917 George Ellery Hale
Andrew Carnegie
3 McDonald Obs. 82-inch[44]
McDonald Observatory
(i.e. Otto Struve Telescope) 		82-inch
210 cm 		2070 m
(6791 ft) 		1939 Otto Struve

See also[edit]

References[edit]

  1. ^"The 200-inch Hale Telescope".astro.caltech.edu.
  2. ^Zirker, J.B. (2005).An acre of glass: a history and forecast of the telescope.Johns Hopkins Univ Press.,p. 317.
  3. ^abKaempffert, Waldemar (December 26, 1948)."Science in Review: Research Work in Astronomy and Cancer Lead Year's List of Scientific Developments".The New York Times(Late City ed.). p. 87.ISSN0362-4331.
  4. ^Schmadel, Lutz (2003-08-05).Dictionary of Minor Planet Names.Springer Science & Business Media.ISBN978-3-540-00238-3.
  5. ^Edison, Hodge (May 1949)."The 200-inch telescope takes its first pictures"(PDF).Engineering and Science Monthly.12(8).
  6. ^"The 200-inch (5.1-meter) Hale Telescope".Palomar Observatory.March 5, 2016.
  7. ^January 26: 60th Anniversary of Hale Telescope "First Light".365daysofastronomy.org (2009-01-26). Retrieved on 2011-07-01.
  8. ^Caltech Astronomy: Palomar Observatory Astronomical Images – Hubble's Variable Nebula NGC 2261Archived2008-10-11 at theWayback Machine.Astro.caltech.edu (1949-01-26). Retrieved on 2011-07-01.
  9. ^abFienberg, Rick (2007-09-14)."Sharpening the 200-inch".Sky and Telescope.Retrieved2016-09-06.
  10. ^120-inch Shane Reflector.Ucolick.org. Retrieved on 2011-07-01.
  11. ^"Palomar FAQ: How far can the Hale telescope see?".Archived fromthe originalon July 11, 2011.
  12. ^Encyclopedia of Astronomy and Physics,"Reflecting Telescopes", Paul Murdin and Patrick Moore
  13. ^Hearst Magazines (July 1931).""Frozen Eye" to bring new worlds into viewPopular Mechanics ".Popular Mechanics.Hearst Magazines. p. 97.
  14. ^"200-inch Hale Telescope, Palomar Observatory".The Top 5 Telescopes of All Time.Space.Archived fromthe originalon 19 August 2009.Retrieved20 December2013.
  15. ^Spencer Jones, H. (1941). "The 200-inch telescope".The Observatory.64:129–135.Bibcode:1941Obs....64..129S.
  16. ^Anderson, John A. (1948). "1948PASP...60..221A Page 222".Publications of the Astronomical Society of the Pacific.60(355): 221.Bibcode:1948PASP...60..221A.doi:10.1086/126043.S2CID121078506.
  17. ^The Hale Reflecting TelescopeCorning Museum of Glass
  18. ^Caltech Astronomy: History: 1908–1949Archived2008-05-11 at theWayback Machine.Astro.caltech.edu (1947-11-12). Retrieved on 2011-07-01.
  19. ^Hearst Magazines (January 1941)."Popular Mechanics".Popular Mechanics.Hearst Magazines. p. 84.
  20. ^Hearst Magazines (April 1936)."Grinder With Human Touch to Polish Eye for Telescope".Popular Mechanics.Hearst Magazines. p. 566.
  21. ^"Mirror, Mirror: Keeping the Hale Telescope optically sharp"by Jim Destefani,Products FinishingMagazine,2008
  22. ^Nickerson, Colin (2007-11-05)."Long time no see".Boston.Boston Globe.Retrieved2009-11-11.
  23. ^"Keck telescope science kit fact sheet, Part 1".SCI Space Craft International. 2009.Retrieved2009-11-11.
  24. ^Bobra, Monica Godha (September 2005).The endless mantra: Innovation at the Keck Observatory(PDF)(Masters).MIT.Archived fromthe original(PDF)on 2011-06-05.Retrieved2009-11-11.
  25. ^Yarris, Lynn (Winter 1992)."Revolution in telescope design debuts at Keck after birth here".Science@Berkeley Lab.Lawrence Berkeley Laboratory.Archived fromthe originalon 2017-12-22.Retrieved2009-11-11.
  26. ^ab"National Park Service: Astronomy and Astrophysics (Palomar Observatory 200-inch Reflector)".nps.gov.Retrieved2019-10-30.
  27. ^"National Park Service: Astronomy and Astrophysics (Palomar Observatory 200-inch Reflector)".
  28. ^MacNeil, Jessica."Hale Telescope takes first photos, January 26, 1949".EDN.Retrieved2019-10-30.
  29. ^Sandage, Allan. (1999). "The first 50 years at Palomar: 1949–1999 the early years of stellar evolution, cosmology, and high-energy astrophysics".Annual Review of Astronomy and Astrophysics.37(1): 445–486.Bibcode:1999ARA&A..37..445S.doi:10.1146/annurev.astro.37.1.445.
  30. ^Wallerstein, George; Oke, J. B. (2000). "The First 50 Years at Palomar, 1949–1999 Another View: Instruments, Spectroscopy and Spectrophotometry and the Infrared".Annual Review of Astronomy and Astrophysics.38(1): 79–111.Bibcode:2000ARA&A..38...79W.doi:10.1146/annurev.astro.38.1.79.
  31. ^Schmidt, Maarten (1963)."3C 273: a star-like object with large red-shift".Nature.197(4872): 1040.Bibcode:1963Natur.197.1040S.doi:10.1038/1971040a0.S2CID4186361.
  32. ^"Comet Halley Recovered".European Space Agency. 2006.Retrieved16 January2010.
  33. ^"Astronomers Find Two Uranus Moons".AP NEWS.Retrieved2019-10-30.
  34. ^Gladman, B. J.;Nicholson, P. D.;Burns, J. A.;Kavelaars, J. J.;Marsden, B. G.;Williams, G. V.;Offutt, W. B.(1998). "Discovery of two distant irregular moons of Uranus".Nature.392(6679): 897–899.Bibcode:1998Natur.392..897G.doi:10.1038/31890.S2CID4315601.
  35. ^Gladman et al. 1998.
  36. ^Lim, L; McConnochie, T; Belliii, J; Hayward, T (2005)."Thermal infrared (8?13?m) spectra of 29 asteroids: The Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey"(PDF).Icarus.173(2): 385.Bibcode:2005Icar..173..385L.doi:10.1016/j.icarus.2004.08.005.Archived fromthe original(PDF)on 2016-03-03.Retrieved2019-08-26.
  37. ^SPACE com Staff (10 December 2009)."New Star Found in Big Dipper".Space.Retrieved2019-10-30.
  38. ^"Jupiter's Smallest Moon".Astrobiology Magazine.2012-06-08.Retrieved2019-11-03.
  39. ^"Update on 'Oumuamua, Our First Interstellar Object".Sky & Telescope.2017-11-10.Retrieved2019-10-30.
  40. ^Masiero, Joseph (2017-10-26). "Palomar Optical Spectrum of Hyperbolic Near-Earth Object A/2017 U1".arXiv:1710.09977[astro-ph.EP].
  41. ^"NASA's Tech Demo Streams First Video From Deep Space via Laser".NASA/JPL-Caltech. December 18, 2023.
  42. ^Thompson, Andrea. (2010-04-14)New method could image Earth-like planets.NBC News. Retrieved on 2011-07-01.
  43. ^"Viewing through 100-inch Hooker Telescope".Mount Wilson Observatory. 2016-06-29.RetrievedJanuary 24,2018.
  44. ^"Otto Struve Telescope".McDonald Observator.RetrievedJanuary 24,2018.

Further reading[edit]

External links[edit]

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