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Reflector telescope.

Reflector telescope.
Reflector telescope.
© National Maritime Museum, London
Repro ID: D3357
Description: This portable reflector telescope is similar to the one used by Cook to observe the transit of Venus. The brass barrel is mounted on a brass pillar with collapsable claw legs. It has adjustable inclination and rotary movement. Attatched to the top of the barrel is a refracting telescopic sight. There is an eyepiece cap and two brass eyepieces. The longer of the two is 97 mm the shorter and more powerful eyepiece is 77 mm. Within the barrel are primary and secondary (objective) specula. Screw thread focusing of the secondary mirror is done through use of the rod attatched to the barrel. There is a spare secondary mirror in a tin box which gives a higher power to each eyepiece. There are five mirrors 1" and 7/8" in diameter. The length with the larger eyepiece is 707 mm. The height to the top of the sight is 550 mm, the diameter of the barrel is 105 mm and has 18" focal length.
Creator: James Short
Date: 1738-68
Credit line: National Maritime Museum, London
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