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The Anglo-Australian Telescope

Anglo-Australian Telescope Commissioned in 1974 (read a brief history), the Anglo-Australian Telescope was one of the last 4-metre equatorially mounted telescopes to be constructed. Its excellent optics, exceptional mechanical stability and precision computer control make it one of the finest telescopes in the world. Also important to the AAT's success has been its suite of state-of-the-art instrumentation, which is constantly being upgraded and improved. Until the 1970s, most of the world largest telescopes had been built in the northern hemisphere. To help redress the balance, the AAT was constructed in Australia so that astronomers could explore in detail some of the most exciting regions of the sky, including the centre of our own Milky Way Galaxy and its nearest neighbours the Magellanic Clouds. Some of the finest globular clusters and nearest radio galaxies can only be seen with difficulty from northern latitudes, if at all.

The AAT can be used in many configurations, each requiring a different instrument or detector to collect and analyse the light. Most astronomers use charge coupled devices (CCDs) to collect data. These highly sensitive solid state devices convert feeble light into digital signals which are then collected and stored on computers for further analysis, rather like an electronic photograph. However, traditional photography is also still used for special projects.

The most commonly used instruments on the AAT are its spectrographs, which split the light from distant objects into its constituent colours. Parts of the resulting spectrum can then be studied in detail to measure important properties such as the temperature, chemical composition, velocity or distance of an object, revealing vital facts about distant stars, galaxies and nebulae that photographs cannot show.

Other specialised instruments collect 'light' energy from the infrared (IR) region of the spectrum and are thus sensitive to the temperature of objects too cool to emit visible light. Using the most recent technical advances, the AAO has taken a lead in designing and building IR instruments, the latest of which, IRIS, provides both images and spectra of the sky. New IR instruments are currently under consideration. Infrared images are especially useful for studying the earliest stages of star formation, normally hidden at visible wavelengths by dust clouds.

Over the past decade the AAO has pioneered the use of optical fibres in astronomy and currently leads the world in this work. The latest of these instruments, the Two-Degree Field facility (or 2dF) uses flexible optical fibres, to collect the light from up to 400 faint stars or galaxies from a two degree field of view. This light is directed to a spectrograph, where the 400 individual spectra are detected by a CCD for analysis. Two degrees of sky is about four Moon diameters across, and is a four-fold increase in area of the AAT prime focus, which was already considered to be wide field for a 4-m telescope. This instrument dramatically improves the efficiency of the telescope, which has traditionally observed one object at a time, allowing astronomers to carry out previously impractical observing projects.

THE AAT: FACTS & FIGURES

ALTITUDE   TELESCOPE  
Base of Dome 1134m Length 15m
Top of Dome 1184m Wgt of central tube/mirrors 116 tonnes
    Wgt with horseshoe mounting 260 tonnes
PRIMARY WINDOW      
Working diameter 3.893m OTHER MIRRORS  
Thickness at outer edge 0.63m Total number 8
Weight 16.19 tonnes Maximum in use at any time 4
Cervit blank cast May 1969 Diameters 0.376-1.47m
Figuring of surface completed June 1973 Weight of largest 860kg
Diameter of central hole 1.067m    
Coated annually 2.5g of aluminium BUILDING  
    Height (to base of dome) 26m
DOME   Diameter 37m
Diameter 37m Depth of excavation 0.3m
Weight 560 tonnes No. of floors or part floors 9
Roatation time 5 min    
Rotates at 32 bogeys   DIRECTORS  
Driven by 4 3.5kW DC motors Dr E J Wampler Sep 1974 - Mar 1976
    Dr D C Morton Jul 1976 - Mar 1986
OBSERVING   Dr R D Cannon Oct 1986 - Sep 1996
Av. clear night time 65% Dr B J Boyle Oct 1996 - Jul 2003
Typical scheduling: Observing 341 nights Prof M M Colless
Jan 2004 -
Instrument tests etc 20 nights    
Aluminising primary mirror 4 nights    
Astronomers using the AAT 250 per year    
For further information, including manuals, observing guides and technical specifications, try the Instruments & Documentation page.