The South African Large Telescope (SALT) is the largest single optical telescope in the Southern Hemisphere, and one of the largest in the world. It is located in Sutherland, South Africa, and is modelled on the design of the Hobby-Eberly Telescope (HET) in Texas. This design has a spherical primary mirror which is fixed in position, with the secondary mirror mounted on a gantry and moving overhead, to aim at different targets. Dr. Bruno Letarte attached a camera to the mirror structure, showing the telescope in operation. He filmed for three days, and compiled the time-lapse video to the left.
SALT’s 11 meter primary mirror is composed of 91 individual hexagonal segments, each of which is 1.2 meters across and mounted on actuators which allow the shape of the mirror to be finetuned from moment to moment. This system, known as Adaptive Optics, allows modern ground-based telescopes to cut through the distortions caused by our constantly shifting atmosphere and produces stunningly sharp images which rival those of space telescopes like the Hubble.