The Lassell reflecting telescope, which had a 24-inch aperture and 20-foot focal length, was built in 1847 for William Lassell (1799-1880), a businessman and astronomer who lived in Starfield near Liverpool. With this telescope Lassell discovered Triton, Neptune's satellite in 1846. It was presented by his daughters to the Royal Observatory in 1883 and it was mounted in this newly-built, 30-foot dome, known as the Lassell Dome. The low-level structure was demolished in the 1890s to make way for the New Physical Laboratory, which reused the dome itself. The dome can therefore still be seen atop the Royal Observatory's South Building.