The Craig telescope was a large telescope built in the 1850s, and while much larger than previous refracting telescopes, it had some problems that hampered its use. Its unique design and potential caused a great deal of excitement in its day. The telescope was ready in August 1852 and was visited by

William Parsons, 3rd Earl of Rosse William Parsons, 3rd Earl of Rosse (17 June 1800 – 31 October 1867), was an Irish astronomer, naturalist, and engineer. He was president of the Royal Society (UK), the most important association of naturalists in the world in the nineteenth ...

, famous for the

Leviathan of Parsonstown Leviathan of Parsonstown, or Rosse six-foot telescope, is a historic reflecting telescope of aperture, which was the largest telescope in the world from 1845 until the construction of the Hooker Telescope in California in 1917. The Rosse six-f ...

, a reflecting telescope and the largest telescope of this age with a six foot mirror.

Telescope

It 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 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 defines an era in modern telescopy in the 19t ...

, a large refracting telescope with an achromatic doublet with an aperture of 61 cm (2 feet or 24 inches) and was completed in 1852 on

Wandsworth Common Wandsworth Common is a public common in Wandsworth, in the London Borough of Wandsworth, south London. It is and is maintained and regulated by Wandsworth Council. It is also a Ward of the London Borough of Wandsworth. The population of the ward ...

and dismantled around 1857 (although the brick tower probably survived until 1870).The Online Museum of the Craig Telescope (www.craig-telescope.co.uk)
/ref> It had a focal length of 76–83 feet. It was named after the Rev. John Craig, who spent a small fortune on it, producing 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 a 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 is optical glass that has relatively high refractive index and low Abbe number (high dispersion). Flint glasses are arbitrarily defined as having an Abbe number of 50 to 55 or less. The currently known flint glasses have refractiv ...

Chance Brothers Chance Brothers and Company was a glassworks originally based in Spon Lane, Smethwick, West Midlands (formerly in Staffordshire), in England. It was a leading glass manufacturer and a pioneer of British glassmaking technology. The Chance fam ...

and a plate glass by

Thames Plate Glass Company Thames Plate Glass Company was a British glass works that operated from 1835 to 1874. Its factories were located at the northern end of Goodluck Hope peninsula, and it was a major employer in Orchard Place district. It demonstrated some very large ...

. The mounting was designed by

William Gravatt William Gravatt FRS (14 July 1806 – 30 May 1866), was a noted English civil engineer and scientific instrument maker. Apprenticed as a mechanical engineer in London from aged 15, after interview he worked with Sir Marc Isambard Brunel on t ...

, 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 Munich ( München) (

Joseph Fraunhofer Joseph Ritter von Fraunhofer (; ; 6 March 1787 – 7 June 1826) was a German physicist and optical lens manufacturer. He made optical glass, an achromatic telescope, and objective lenses. He also invented the spectroscope and developed diffra ...

's firm), one at

Pulkovo Observatory The Pulkovo Astronomical Observatory (russian: Пулковская астрономическая обсерватория, Pulkovskaya astronomicheskaya observatoriya), officially named the Central Astronomical Observatory of the Russian Academ ...

in Europe and one at

Harvard College Observatory The Harvard College Observatory (HCO) 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, United St ...

in America. The largest telescope at the time was in Ireland, a 6-foot (183 cm) aperture

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

mirror by

. (see "

") One of the goals for the telescope was to look for a possible moon of Venus and to confirm the third (Crepe) ring of saturn. Some of the reported issues were with the overall lens quality and troubles in the personal life of Craig.

References

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External links

*https://web.archive.org/web/20100504160637/http://homepage.ntlworld.com/greg.smyerumsby/craig/ Telescopes

Telescope

See also

References

Further reading

External links