The Anglo-Australian Telescope (AAT) was built in Australia in the 1970s. At that time, most large telescopes were in the Northern Hemisphere. The AAT was built to provide more access for astronomers in the Southern Hemisphere. To begin with it was jointly owned by Australia and the UK. Now it is owned by Australia. The AAT is still doing important science and remains one of the world's most productive telescopes.
The AAT's location lets astronomers observe extremely dark skies. It is 1,130 metres above sea level in remote Siding Spring Mountain. Siding Spring is located around 500 km to the north-west of Sydney, Australia. The southern skies are where some of the most exciting objects are found. Sights like the centre of our own Milky Way galaxy and our galactic neighbours, the Magellanic Clouds.
The AAT has a 3.9 metre primary mirror. Its total mass is 120 metric tonnes. It is still the largest visible light telescope in Australia. Its wide field of view have given us some of the most stunning pictures of the night sky. Images which have been published across the world.
The AAT was one of the last 4 metre equatorially mounted telescopes to be constructed. Telescopes like this are tilted in line with the rotation of the Earth. This lets them follow or track a star through the sky more easily as they only have to move in one direction. Most modern large telescopes must move in two directions to follow a star. This is more complex, but modern computers make it possible.