The Radcliffe 18/24 inch twin refractor is two telescopes in one. The 18 inch telescope was originally used to guide the telescope, though modern electronic guiding mechanisms mean this is no longer necessary. The telescope was built in 1901 for the University of Oxford's Radcliffe Observatory. It has been at the University of London Observatory since 1938. Originally used to make images on photographic plates, the telescope now has a modern CCD digital detector.