A submillimetre-wave telescope located at the Mauna Kea Observatories on the island of Hawaii. It is managed by the Joint Astronomy Center, Hilo, Hawaii, on behalf of the UK, the Netherlands and Canada, which are the sponsoring countries. It is a Cassegrain design, with a paraboloidal reflector 15 metres 49 feet in diameter. The dish is constructed from 276 lightweight panels supported on a mild steel frame, designed to deform uniformly and so maintain the paraboloid shape when the orientation is changed. The mount is altazimuth. The telescope is inside a rotating protective enclosure; during observations, the viewing aperture is covered with a membrane of woven teflon to protect the surface from wind and heating by the Sun. Only 10 per cent of the submillimetre radiation is absorbed by the membrane. The telescope’s capabilities were extended in 1996 by the provision of a newly developed instrument, which is a combined imaging camera and photometer. Known as SCUBA Submillimetre Common-User Bolometer Array, it consists of two arrays of detectors cooled to below 0.1 K. One array is optimized for use at 850 microns and the other at 450 microns.