The Anglo-Australian
Telescope, a reflecting telescope with a mirror 3.9 m (153 in) in diameter, is located with other Australian
and British instruments at Siding Spring
Observatory in the Warrumbungle Range near Coonabarabran, New South Wales, 400 km (250 mi) northwest of Sydney. The
telescope began operating in 1975. The observatory, a major astronomical research center, sits at an altitude of 1,160 m (3,805 ft). The United Kingdom Schmidt telescope, also there, is a near-twin of the 48-in (122-cm) Schmidt at Palomar Mountain, Calif. It has been used to complete an important reference survey by photographing all the sky that is too far south to be seen from Palomar.