40-foot telescope: Difference between revisions
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The telescope was located on the grounds of [[Observatory House]], Herschel's house in Slough, between 1789 and 1840.<ref name="nmm" /> The [[first light|first observation with the telescope]] was in 1787, when Herschel pointed the then-incomplete telescope towards the [[Orion nebula]], which he observed by crawling into the telescope and using a hand-held [[eyepiece]].<ref name="making" /> The one achievement of the telescope was to discover [[Enceladus (moon)|Enceladus]] and [[Mimas (moon)|Mimas]], the 6th and 7th [[moons of Saturn]], although this is not certain, as Herschel used other telescopes at the same time.<ref name="nmm" /> |
The telescope was located on the grounds of [[Observatory House]], Herschel's house in Slough, between 1789 and 1840.<ref name="nmm" /> The [[first light|first observation with the telescope]] was in 1787, when Herschel pointed the then-incomplete telescope towards the [[Orion nebula]], which he observed by crawling into the telescope and using a hand-held [[eyepiece]].<ref name="making" /> The one achievement of the telescope was to discover [[Enceladus (moon)|Enceladus]] and [[Mimas (moon)|Mimas]], the 6th and 7th [[moons of Saturn]], although this is not certain, as Herschel used other telescopes at the same time.<ref name="nmm" /> |
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As part of the funding deal with the telescope, [[Caroline Herschel]] was |
As part of the funding deal with the telescope, [[Caroline Herschel]] was granted a pension of £50 per year to be William's assistant. As a result, she was the first woman in England to be paid to carry out astronomy.<ref name="nmm" /> |
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The telescope was a local tourist attraction,<ref name="nmm_image" /> visited by rich and famous people on their way to the nearby [[Windsor Castle]] to visit the King,<ref name="ssplprint" /> and was featured on [[Ordinance Survey]] maps.<ref name="nmm_image">{{cite web | url=http://www.nmm.ac.uk/collections/explore/object.cfm?ID=ZBA4492 | title=Herschel's Grand Forty feet Reflecting Telescopes (ZBA4492) | publisher=National Maritime Museum | accessdate=22 November 2008}}</ref> It was the largest telescope in the world for 50 years.<ref name="nmm" /> |
The telescope was a local tourist attraction,<ref name="nmm_image" /> visited by rich and famous people on their way to the nearby [[Windsor Castle]] to visit the King,<ref name="ssplprint" /> and was featured on [[Ordinance Survey]] maps.<ref name="nmm_image">{{cite web | url=http://www.nmm.ac.uk/collections/explore/object.cfm?ID=ZBA4492 | title=Herschel's Grand Forty feet Reflecting Telescopes (ZBA4492) | publisher=National Maritime Museum | accessdate=22 November 2008}}</ref> It was the largest telescope in the world for 50 years.<ref name="nmm" /> |
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Revision as of 14:41, 27 November 2008
William Herschel's 40-foot telescope, also known as the Great Forty-Foot telescope, was an optical telescope constructed between 1785 and 1789 at Observatory House in Slough, England. It may have been used to discover Enceladus and Mimas, the 6th and 7th moons of Saturn. It was dismantled in 1840; today the original mirror and a 10 foot section of the tube remains.
Construction
The telescope was constructed by Sir William Herschel, with the assistance of Johann Herschel and Caroline Herschel, between 1785 and 1789 in Slough, with components made in Clay Hall near Windsor. The tube was made of iron. It was paid for by King George III, who granted £4,000 for it to be made.[1]
Two 48-inch (120 cm) concave metal mirrors were made for the telescope. The first was cast in a London foundry in 1785, and was made of speculum (an alloy of mostly copper and tin) with arsenic to improve the finish. The mirror weighed half a ton, but was too thin to hold its shape once it had been ground and polished. A second mirror with twice the thickness of the original was cast a few years later, and this was used rather than the original. However, this required more frequent polishing due to its different composition, and the original mirror was used when the second was being polished. The mirrors remained the largest in the world until 1845.[2][3]
Use
The telescope was located on the grounds of Observatory House, Herschel's house in Slough, between 1789 and 1840.[1] The first observation with the telescope was in 1787, when Herschel pointed the then-incomplete telescope towards the Orion nebula, which he observed by crawling into the telescope and using a hand-held eyepiece.[3] The one achievement of the telescope was to discover Enceladus and Mimas, the 6th and 7th moons of Saturn, although this is not certain, as Herschel used other telescopes at the same time.[1]
As part of the funding deal with the telescope, Caroline Herschel was granted a pension of £50 per year to be William's assistant. As a result, she was the first woman in England to be paid to carry out astronomy.[1]
The telescope was a local tourist attraction,[4] visited by rich and famous people on their way to the nearby Windsor Castle to visit the King,[2] and was featured on Ordinance Survey maps.[4] It was the largest telescope in the world for 50 years.[1]
Due to problems with the mirrors and because the telescope was unwieldly, the telescope did not prove to be a substantial improvement over smaller telescopes.[3] The final observation made by the telescope was in 1815.[1]
Decommissioning
The telescope's frame was dismantled in 1840 by William Herchel's son, John Herschel,[1] on his return from carrying out observations in South Africa. It was dismantled as it was feared that the frame might collapse due to rot, and John feared for the safety of his young children. A small ceremony was conducted to commemorate its dismantling.[5]
The tube was left lying in the garden, where 30 years later the tube was crushed by a falling tree. The remaining piece of the tube is a 10 foot length of the speculum end, which is 3048 by 1465 mm. This was still located in the garden of Observatory House in 1955[6], but was subsequently moved and is now located in the Herschel Collection of the National Maritime Museum, Greenwich, London.[1] The original mirror cast for the telescope now resides in the Science Museum, London.[7]
References
- ^ a b c d e f g h "40-foot Herschelian (reflector) telescope tube remains (AST0947)". National Maritime Museum. Retrieved 22 November 2008.
- ^ a b "Original mirror for William Herschel's 40 foot telescope, 1785". Science & Society Picture Library. Retrieved 22 November 2008.
- ^ a b c "Original mirror for William Herschel's 40-foot telescope, 1785". The Science Museum. 2004. Retrieved 2008-11-22.
- ^ a b "Herschel's Grand Forty feet Reflecting Telescopes (ZBA4492)". National Maritime Museum. Retrieved 22 November 2008.
- ^ "'Slough. The 40ft reflector with all the woodwork down' (PAF7451)". National Maritime Museum. Retrieved 22 November 2008.
- ^ Berendzen, Richard (1976). Man Discovers the Galaxies. Science History Publications. pp. pp.12–13. ISBN 0-88-202-023-4.
{{cite book}}:|pages=has extra text (help); Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Original mirror for William Herschel's forty-foot telescope, 1785". Science Museum]]. Retrieved 2008-11-23.