Editing Anglo-Australian Telescope

{{Short description|Australian Astronomical Observatory telescope}}
{{Use Australian English|date=April 2018}}
{{Use dmy dates|date=April 2018}}
{{Infobox telescope}}
The '''Anglo-Australian Telescope''' ('''AAT''') is a 3.9-metre [[Equatorial mount|equatorially mounted]] telescope operated by the [[Australian Astronomical Observatory]] and situated at the [[Siding Spring Observatory]], Australia, at an altitude of a little over 1,100&nbsp;m. In 2009, the telescope was ranked as having the fifth-highest-impact of the world's optical telescopes. In 2001–2003, it was considered the most scientifically productive 4-metre-class optical telescope in the world based on scientific publications using data from the telescope.<ref>{{cite news |last=Watson |first=Fred |title=Across the universe |url=http://www.smh.com.au/news/national/across-the-universe/2009/01/05/1231003937356.html |newspaper=[[The Sydney Morning Herald]] |date=6 January 2009 |access-date=8 November 2011}}</ref><ref>{{cite web |last=Plonter |first=Tammy |title=Australian Telescope Leads the World in Astronomy Research |url=http://www.universetoday.com/17930/australian-telescope-leads-the-world-in-astronomy-research/ |work=Universe Today |date=11 September 2008}}</ref>

The telescope was commissioned in 1974 with a view to allowing high-quality observations of the sky from the Southern Hemisphere. At the time, most major telescopes were located in the Northern Hemisphere, leaving the southern skies poorly observed.<ref name="asitm">{{cite book |title=Australian Science in the Making |last=Home |first=Roderick Weir |date=1990 |publisher=[[Cambridge University Press]] |isbn=0521396409 |page=360 |url=https://books.google.com/books?id=w4oY-w1I3GsC |access-date=6 December 2015}}</ref> It was the largest telescope in the Southern Hemisphere from 1974 to 1976, then a close second to the [[Víctor M. Blanco Telescope]] from 1976 until 1998, when the first ESO [[Very Large Telescope]] (VLT) was opened. The AAT was credited with stimulating a resurgence in British optical astronomy.<ref name="asitm"/> It was built by the United Kingdom in partnership with Australia but has been entirely funded by Australia since 2010.<ref>{{cite web |last=Lomb |first=Nick |title=Australia's largest optical telescope to become part of the Australian Astronomical Observatory on 1 July 2010 and to celebrate its 36th birthday |url=http://www.sydneyobservatory.com.au/2010/australias-largest-optical-telescope-to-become-the-australian-astronomical-observatory-on-1-july-2010-and-to-celebrate-its-36th-birthday/ |work=Sydney Observatory |date=15 June 2010}}</ref> Observing time is available to astronomers worldwide.

The AAT was one of the last large telescopes built with an [[equatorial mount]]. More recent large telescopes have instead adopted the more compact and mechanically stable [[altazimuth mount]]. The AAT was, however, one of the first telescopes to be fully computer-controlled, and set new standards for pointing and tracking accuracy.

== History ==
British astronomer [[Richard van der Riet Woolley]] pushed for a large optical telescope for the Southern Hemisphere in 1959.<ref name="asitm"/> In 1965, [[Macfarlane Burnet]], president of the [[Australian Academy of Science]], wrote to the federal education minister [[John Gorton]] inviting the federal government to support a joint British-Australian telescope project. Gorton was supportive, and nominated the [[Australian National University]] and [[CSIRO]] as Australia's representatives in the joint venture; he was unsuccessful in his attempts to induce [[NASA]] to join the project. Gorton brought the proposal before cabinet in April 1967, which endorsed the scheme and agreed to contribute half the capital and running costs. An agreement with the British was finalised a few weeks later and a Joint Policy Committee started work on construction planning in August 1967.<ref>{{cite book |last=Hancock |first=Ian |title=John Gorton: He Did It His Way |publisher=Hodder |year=2002 |pages=120–121}}</ref> It took until September 1969 for plans to be finalised.<ref name="fhu">{{cite book |title=Fred Hoyle's Universe |last=Gregory |first=Jane |date=2005 |publisher=[[Oxford University Press]] |isbn=0191578460 |page=[https://archive.org/details/fredhoylesuniver0000greg/page/225 225] |url=https://archive.org/details/fredhoylesuniver0000greg |url-access=registration |access-date=15 April 2013}}</ref> The agreement initially committed the specification to a telescope design based on the American [[Kitt Peak National Observatory|Kitt Peak]] telescope until its deficiencies were known. Both the [[Horseshoe mounting|horseshoe mount]] and the gearing system needed improvements.<ref name="eotss">{{cite book |last=Haynes |first=Raymond |title=Explorers of the Southern Sky: A History of Australian Astronomy |url=https://books.google.com/books?id=XoeiJxMmXZ8C |publisher=Cambridge University Press |date=1996 |pages=382–394 |access-date=15 April 2013 |isbn=0521365759}}</ref> Although the revised gear system was considerably more expensive it was significantly more accurate, lending itself well to future applications.<ref name="eotss" />

The mirror blank was made by [[Owens-Illinois]] in Toledo, Ohio. It was then transported to Newcastle, England, where [[Sir Howard Grubb, Parsons and Co]] took two years to grind and polish the mirror's surface.<ref name="eotss" /> [[Mitsubishi Electric]] built the mount which was constructed by August 1973. [[First light (astronomy)|First light]] occurred on 27 April 1974. The telescope was officially opened by [[Charles, Prince of Wales|Prince Charles]] on 16 October 1974.<ref name="eotss" />

== Structure and telescope ==
The telescope is housed within a seven-story, circular, concrete building topped with a 36m diameter rotating steel dome. It was designed to withstand the high winds prevailing at that location. The slit is narrow. The dome is required to move with the telescope to avoid obstruction.<ref name="eotss" /> The top of the dome is 50m above ground level.

The telescope tube structure is supported inside a massive 12m diameter horseshoe, which rotates around the polar axis (parallel to Earth's axis) for tracking the sky. The total moving mass is 260 tonnes.<ref>{{cite web |title=The Anglo-Australian Telescope |url=https://www.aao.gov.au/about-us/AAT |access-date=27 April 2018 |archive-date=9 January 2021 |archive-url=https://web.archive.org/web/20210109052220/https://www.aao.gov.au/about-us/AAT |url-status=dead }}</ref>

The telescope has various foci for flexible instrumentation: originally there were three top-end rings which can be exchanged using the dome crane during the daytime. One was for f/3.3 prime-focus, with corrector lenses and a cage for a human observer taking photographs (rarely used after the 1980s); one has a large secondary mirror giving an f/8 [[Cassegrain reflector|Cassegrain]] focus; and a third top-end has smaller f/15 and f/36 secondary mirrors. A fourth top-end was built in the 1990s to give a 2-degree field of view at prime focus, with 400 optical fibres feeding the 2dF instrument and its later enhancements [[AAOmega spectrograph|AAOmega]] and HERMES.

== Instruments ==
[[Image:Anglo-Australian telescope at Siding Springs Observatory.jpg|thumb|upright|3.9-metre equatorially mounted telescope]]
The AAT is equipped with a number of instruments, including:
* The Two Degree Field facility ([[2dF instrument|2dF]]), a robotic [[optical fiber|optical fibre]] positioner for obtaining [[spectroscopy]] of up to 400 objects over a 2° [[field of view#Astronomy|field of view]] simultaneously.
* The [[University College London]] Échelle Spectrograph (UCLES), a high-resolution optical spectrograph which has been used to discover many [[extrasolar planets]]. 
* IRIS2, a wide-field [[infrared astronomy|infrared]] camera and spectrograph.
* HERMES, a high resolution spectrograph to be used with the 2dF positioner, commissioned in 2015.<ref name=HERMES>{{cite web |title=HERMES project AAT |url=http://www.aao.gov.au/HERMES/ |publisher=Department of Industry, Innovation, Climate Change, Science, Research and Tertiary Education |access-date=15 April 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130409142618/http://www.aao.gov.au/HERMES/ |archive-date=9 April 2013}}</ref> HERMES is mainly being used for the 'Galactic Archaeology with Hermes' (GALAH) Survey, which aims to reconstruct the history of our galaxy's formation from precise multi-element (~25 elements) abundances of 1&nbsp; million stars derived from HERMES spectra.
*TAIPAN, a multispectral positioner and spectrograph (successor to HERMES and 2dF) which uses starbugs, small robots that move into position by vibrating, to position optical fibres.<ref>{{cite web|url=https://www.unsw.edu.au/newsroom/news/2018/02/robotic--starbugs--technology-to-survey-millions-of-stars |publisher=UNSW |title=Robotic 'Starbugs' technology to survey millions of stars |first1=Deborah |last1=Smith |date=2018-02-01 |access-date=2025-04-14}}</ref>

=== Comparisons ===

{| class="wikitable sortable" style="text-align: center; font-size: 0.9em;"
|+Largest optical astronomical telescopes in the late 1970s
|-
! width=18 | #
! Name /<br>Observatory
! style="width:40px;" | Image
! Aperture
! width=60 | M1<br>Area 
! Altitude
! width=60 | First<br>Light 
|- 
| {{small|1.}}
| align=left | [[BTA-6]]<br>{{small|([[Special Astrophysical Observatory of the Russian Academy of Science|Special Astrophysical Obs]])}}
| bgcolor=#ddd | [[File:Big asimutal teleskop.jpg|80px]]
| 238&nbsp;inch<br>605&nbsp;cm
| 26&nbsp;m<sup>2</sup> 
| {{convert|2070|m|ft|abbr=on}}
| 1975
|-
| {{small|2.}}
| align=left | [[Hale Telescope]]<br>({{small|[[Palomar Observatory]]}})
| bgcolor=#ddd | [[File:P200 Dome Open.jpg|80px]]
| 200&nbsp;inch<br>508&nbsp;cm
| 20&nbsp;m<sup>2</sup>
| {{convert|1713|m|ft|abbr=on}}
| 1949
|-
| {{small|3.}}
| align=left | [[Nicholas U. Mayall Telescope|Mayall Telescope]]<br>{{small|([[Kitt Peak National Observatory|Kitt Peak National Obs.]])}}
| bgcolor=#ddd | [[File:Kittpeakteliscope.JPG|80px]]
| 158&nbsp;inch<br>401&nbsp;cm 	
| 10&nbsp;m<sup>2</sup>
| {{convert|2120|m|ft|abbr=on}} <!-- alt. for telescope not obs! --> 
| 1973
|-
| {{small|4.}}
| align=left | [[Víctor M. Blanco Telescope]]<br>{{small|([[Cerro Tololo Inter-American Observatory|CTIO Observatory]])}}
| bgcolor=#ddd | [[File:4m-Victor M. Blanco Telescope cropped.jpg|80px]]
| 158&nbsp;inch<br>401&nbsp;cm 	
| 10&nbsp;m<sup>2</sup>
| {{convert|2200|m|ft|abbr=on}}
| 1976
|-bgcolor=#edf3fe
| {{small|5.}}
| align=left | '''Anglo-Australian Telescope'''<br>{{small|([[Siding Spring Observatory]])}}
| bgcolor=#ddd | [[File:Anglo-Australian Telescope dome.JPG|80px]]
| 153&nbsp;inch<br>389&nbsp;cm 
| 12&nbsp;m<sup>2</sup>
| {{convert|1742|m|ft|abbr=on}}
| 1974
|- 
| {{small| 6.}}
| align=left | [[ESO 3.6 m Telescope]]<br>{{small|([[La Silla Observatory]])}}
| bgcolor=#ddd | [[File:Wallpaper of 3.6-m Telescope at La Silla.jpg|80px]]
| 140&nbsp;inch<br>357&nbsp;cm
| 8.8&nbsp;m<sup>2</sup><!-- 8.8564 m2 -->
| {{convert|2400|m|ft|abbr=on}}
| 1976
|-
| {{small|7.}}
| align=left | [[C. Donald Shane telescope|Shane Telescope]]<br>{{small|([[Lick Observatory]])}}
| bgcolor=#ddd | [[File:Shane dome.JPG|80px]]
| 120&nbsp;inch<br>305&nbsp;cm
| ~7&nbsp;m<sup>2</sup>
| {{convert|1283|m|ft|abbr=on}}
| 1959
|}

== See also ==
*[[List of largest optical reflecting telescopes]]
*[[List of largest optical telescopes in the 20th century]]
{{clear}}

== References ==
{{reflist|30em}}

== External links ==
{{Commons}}
* {{Official website|1=http://www.aao.gov.au/about/aat.html}}
* [http://janus.lib.cam.ac.uk/db/node.xsp?id=EAD%2FGBR%2F0180%2FRGO%2047 Online catalogue of building project papers (part of the Royal Greenwich Observatory Archives held at Cambridge University Library)]
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[[Category:Reflecting telescopes]]
[[Category:Siding Spring Observatory]]
[[Category:1974 establishments in Australia]]
[[Category:Australia–United Kingdom relations]]