Largest fully-steerable radio telescope

The largest fully steerable radio telescope is the Green Bank Telescope in West Virginia, USA. The main dish has a diameter of 100 m (328 ft) with a 60 m (196 ft) support boom that holds the receiving antennas. The combined weight of the dish and its steel-frame azimuth-elevation mounting is 7,600 tonnes (8,400 tons). The telescope saw first light on 23 August 2000.

In the context of radio telescopes, "fully steerable" means that its operators can rotate and elevate the dish to point at any section of the sky. The entire structure can rotate 360 degrees, and its dish can be elevated between 5 and 95 degrees. Larger radio telescopes, such as the FAST Observatory in China or the now-defunct Arecibo Telescope in Puerto Rico, have a fixed dish that can be focused on a narrower range of targets by moving the receiving antenna around.

The dish at Green Bank is designed to focus incoming signals to a point that is significantly offset from its centre. This means that its view of the cosmos is not partially blocked by its own receiver and boom.