Replica of the hand-operated,speculum grinding/polishing machine designed and constructed by William Herschel,circa 1780,to produce high-quality parabolic mirrors for the many 7-foot reflector telescopes constructed in his workshop at New King Street,Bath. These small,parabolic mirrors,with an aperture of around 150mm (6-inches),were shaped and polished by Herschel from the castings that he made in speculum alloy. A 7-foot Newtonian-type reflector telescope,using a 6.2 inch diameter paraboloidal mirror,was used in Herschel's detailed stellar survey and led to his discovery of the planet Uranus in 1781 |