40-foot telescope
Created: February 1787 (First Light)
Creator: William Herschel Location: Slough, England Stats: Primary Mirror: 1.2 m (diameter) Light Collecting Area: 1.1 m squared Light Gathering Power: 57600x human eye Focal Length: 12.2 m Focal Ratio: f/10 Wavelength: Optical Type: Reflector |
History:
The 40-foot telescope, also known as the Great Forty-Foot, was built from1785-1798 and remained in use till 1839. It was built by Sir William Herschel, and was made of copper, tin, iron, clay, and mirrors. It sit on a alt-azimuth mounting and was considered the largest telescope in the world for over 50 years where it was overtaken by Lord Rosse's telescope in 1845. The greatest achievement of the telescope was that it was used to discover Enceladus and Mimas, two of Saturn's moons. The telescope lacked other significant findings, but it served largely as an icon for astronomers based on its size. While it was in operation it became a tourist attraction, drawing in those on their way to visit Windor Castle, a nearby castle the King of England lived in. In 1839 William Herschel's son, John Herschel decided to decommission the telescope in fear of the frame rotting and collapsing. A piece of the tube that housed the mirrors in the telescope was brought to the Observatory House in 1955 but has since been moved to the Royal Observatory in Greenwich, London. |