Model telescope

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William Parsons, 3rd Earl of Rosse (1800-67) experimented with fluid lenses and made great improvements in casting telescope specula. This is a contemporary model of his reflecting telescope with a three foot diameter (90 cm) speculum. Its tube was 26 feet (7.9m) long, and it was completed in 1840 in the grounds of his Irish home, Birr Castle.

This wooden model was probably used in lectures by an owner and supporter of the Earl of Rosse. It shows the famous 36-inch (90 cm) reflecting telescope at Birr, the largest in the world until the Earl of Rosse completed a second instrument at Birr, which was twice the size, in 1845.

The Earl of Rosse made careful metallurgical tests, and discovered that if the mirror were cooled slowly in an annealing furnace, a higher tin content, producing a brighter surface, could be produced. He also used a steam-driven machine to grind and polish the mirrors. His telescopes produced a new view of the heavens, but were limited by being positioned in one of the wettest parts of these islands.

Record details

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• Online ID: 000-180-001-220-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland Part 2
  Project description   View all records in project
• Ref: National Museums Scotland  T.1911.160
• Date: Around 1840
  
• Material: Telescope / model
  
• Dimensions:
• What: Telescope / model
  
• Subject: 3. ASTRONOMY, Telescopes (Departmental Classification)
  22. PHYSICS, Light (Departmental Classification)
  
• Who: Lord Rosse (Owner ? of original telescope)
  
• Where: Ireland, County Offaly, Birr
  
• Event:
• Description: Model of Lord Rosse's telescope showing the method of mounting it, made at Birr Castle, Ireland
  
• References:
  • C. Mollan, W. Davis, B. Finucane (eds.), Some People and Places in Irish Science and Technology (Dublin, 1985), pp 84-7 
  • J.E. Burnett and A.D. Morrison-Low, Vulgar & Mechanick:the Scientific Instrument Trade in Ireland 1650-1921 (Edinburgh and Dublin, 1989), pp 89-94;Lord Oxmantown, 'Account of a series of experiments on the construction of large reflecting telescopes', Ed 
  • Patrick Moore, The Astronomy of Birr Castle (London, 1971) 
• Translations:
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