Refractors were the earliest type of optical telescope. Sighting was usually by optical telescope. One part of JWST development was the production of the Optical Telescope Element Pathfinder. Two lenses at this separation form the simplest type of optical telescope. The resulting large redshift make them difficult targets with an optical telescope. Both SALT and HET have an unusual design for an optical telescope. MSSL engineers participated in building and testing the Ultraviolet Optical Telescope (UVOT) instrument on Swift. Ball Aerospace has been subcontracted to develop and build the Optical Telescope Element (OTE). For observation purposes, the optimal location for an optical telescope is undoubtedly in outer space. It has the largest monolithic, or , in an optical telescope. SALT is the largest optical telescope in the southern hemisphere. Starting from 1994, the observatory owns an optical telescope. During launch it is wrapped around the Optical Telescope Element and then later is unfolded. It hosts the Southern African Large Telescope, the largest optical telescope in the Southern Hemisphere. It hosts the Southern African Large Telescope, the largest optical telescope in the southern hemisphere.