The Anglo-Australian Telescope (AAT) is a 3.9-metre 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 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.
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. 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. 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. It took until September 1969 for plans to be finalised. The agreement initially committed the specification to a telescope design based on the American Kitt Peak telescope until its deficiencies were known. Both the horseshoe mount and the gearing system needed improvements. Although the revised gear system was considerably more expensive it was significantly more accurate, lending itself well to future applications.
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 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 and HERMES.
Instruments and Programs
thumb|upright|3.9-metre equatorially mounted telescope
The AAT is equipped with a number of instruments, including:
- The Two Degree Field facility (2dF), a robotic optical fibre positioner for obtaining spectroscopy of up to 400 objects over a 2° field of view simultaneously. A 2dF and AAOmega program called OzDES ran for six years to obtain redshifts in the Dark Energy Survey (DES) observing fields for tens and thousands of galaxies, as well as obtain spectra of supernovae and other transients.
- 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 camera and spectrograph.
- HERMES, a high resolution spectrograph to be used with the 2dF positioner, commissioned in 2015. 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 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.
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
|-
|
| align=left | BTA-6<br>
| bgcolor=#ddd | 80px
| 238 inch<br>605 cm
| 26 m<sup>2</sup>
|
| 1975
|-
|
| align=left | Hale Telescope<br>()
| bgcolor=#ddd | 80px
| 200 inch<br>508 cm
| 20 m<sup>2</sup>
|
| 1949
|-
|
| align=left | Mayall Telescope<br>
| bgcolor=#ddd | 80px
| 158 inch<br>401 cm
| 10 m<sup>2</sup>
| <!-- alt. for telescope not obs! -->
| 1973
|-
|
| align=left | Víctor M. Blanco Telescope<br>
| bgcolor=#ddd | 80px
| 158 inch<br>401 cm
| 10 m<sup>2</sup>
|
| 1976
|-bgcolor=#edf3fe
|
| align=left | Anglo-Australian Telescope<br>
| bgcolor=#ddd | 80px
| 153 inch<br>389 cm
| 12 m<sup>2</sup>
|
| 1974
|-
|
| align=left | ESO 3.6 m Telescope<br>
| bgcolor=#ddd | 80px
| 140 inch<br>357 cm
| 8.8 m<sup>2</sup><!-- 8.8564 m2 -->
|
| 1976
|-
|
| align=left | Shane Telescope<br>
| bgcolor=#ddd | 80px
| 120 inch<br>305 cm
| ~7 m<sup>2</sup>
|
| 1959
|}
See also
- List of largest optical reflecting telescopes
- List of largest optical telescopes in the 20th century
References
External links
- Online catalogue of building project papers (part of the Royal Greenwich Observatory Archives held at Cambridge University Library)