Craig telescope
Encyclopedia
The Craig telescope was the largest refracting telescope (a telescope with a lens) in the world from 1852 to 1857, erected near London, England. It was a great refractor
, a large refracting telescope with an achromatic doublet with an aperture of 61 cm (2 feet (24 inches)) and that was completed in 1852 in Wandsworth Common
and dismantled around 1857 (although the brick tower probably survived until 1870). Its namesake, the Rev. John Craig, spent a small fortune to produce a uniquely designed telescope with nearly double the aperture of the next largest refracting telescopes, making it the largest refracting telescope in the World for the better part of a decade. However, it had problem with its lens figuring starting from its first light in the summer of 1852.It soon fell into disuse as that same year Craig lost his only son, then his wife in 1854, and lost his brother and was put in jail for 6 weeks in 1856.
Craig did not have the lens re-figured and the telescope struggled to achieve his modest goals, which included observations of Earth's Moon and Saturn. It was eventually demolished and Craig moved on to other projects, including opening one of the first indoor skating rinks.
The doublet was made with flint glass
by Chance Brothers
and a plate glass by Thames Plate Glass Company. The mounting was designed by William Gravatt, and featured a 19.5 meter tall brick tower with a 24.5 m long cigar shaped telescope tube (built by Messrs Rennie) slung from the side.
The next largest refractors were two 15 inch (38 cm) refractors built by Merz and Mahler of Münich (Joseph Fraunhofer's firm), one at Pulkovo Observatory
in Europe and one at Harvard College Observatory
in America. The largest telescope at the time was in Ireland, a 6 foot (183 cm) aperture metal
mirror by William Parsons, 3rd Earl of Rosse
. (see "Leviathan of Parsonstown
")
Great refractor
Great refractor refers to a large telescope with a lens, usually the largest refractor at an observatory with an equatorial mount. The preeminence and success of this style in observational astronomy was an era in telescope use in the 19th and early 20th century. Great refractors were large...
, a large refracting telescope with an achromatic doublet with an aperture of 61 cm (2 feet (24 inches)) and that was completed in 1852 in Wandsworth Common
Wandsworth Common
Wandsworth common is a public common in Wandsworth, south London. It is close to Clapham Common and Wandsworth Common railway station. It is wholly in the London borough of Wandsworth...
and dismantled around 1857 (although the brick tower probably survived until 1870). Its namesake, the Rev. John Craig, spent a small fortune to produce a uniquely designed telescope with nearly double the aperture of the next largest refracting telescopes, making it the largest refracting telescope in the World for the better part of a decade. However, it had problem with its lens figuring starting from its first light in the summer of 1852.It soon fell into disuse as that same year Craig lost his only son, then his wife in 1854, and lost his brother and was put in jail for 6 weeks in 1856.
Craig did not have the lens re-figured and the telescope struggled to achieve his modest goals, which included observations of Earth's Moon and Saturn. It was eventually demolished and Craig moved on to other projects, including opening one of the first indoor skating rinks.
The doublet was made with flint glass
Flint glass
Flint glass is optical glass that has relatively high refractive index and low Abbe number. Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractive indices ranging between 1.45 and 2.00...
by Chance Brothers
Chance Brothers
Chance Brothers and Company was a glassworks originally based in Spon Lane, Smethwick, West Midlands , in England. It was a leading glass manufacturer and a pioneer of British glassmaking technology....
and a plate glass by Thames Plate Glass Company. The mounting was designed by William Gravatt, and featured a 19.5 meter tall brick tower with a 24.5 m long cigar shaped telescope tube (built by Messrs Rennie) slung from the side.
The next largest refractors were two 15 inch (38 cm) refractors built by Merz and Mahler of Münich (Joseph Fraunhofer's firm), one at Pulkovo Observatory
Pulkovo Observatory
The Pulkovo Astronomical Observatory астрономи́ческая обсервато́рия Росси́йской акаде́мии нау́к), the principal astronomical observatory of the Russian Academy of Sciences, located 19 km south of Saint Petersburg on Pulkovo Heights...
in Europe and one at Harvard College Observatory
Harvard College Observatory
The Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, USA, and was founded in 1839...
in America. The largest telescope at the time was in Ireland, a 6 foot (183 cm) aperture metal
Speculum metal
Speculum metal is a mixture of around two-thirds copper and one-third tin making a white brittle alloy that can be polished to make a highly reflective surface. It is used primarily to make different kinds of mirrors including early reflecting telescope optical mirrors...
mirror by William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse, Knight of the Order of St Patrick was an Irish astronomer who had several telescopes built. His 72-inch telescope "Leviathan", built 1845, was the world's largest telescope until the early 20th century.-Life:He was born in Yorkshire, England, in the city of...
. (see "Leviathan of Parsonstown
Leviathan of Parsonstown
Leviathan of Parsonstown is the unofficial name of the Rosse six foot telescope. This is a historic reflecting telescope of 72 in aperture, which was the largest telescope in the world from 1845 until the construction of the 100 in Hooker Telescope in 1917...
")
Further reading
External links
- The Online Museum of the Craig Telescope (www.craig-telescope.co.uk)
- http://homepage.ntlworld.com/greg.smyerumsby/craig/