Portable telescope
This non-achromatic telescope has three draw tubes. The barrel is made of pasteboard and is decorated with hand-painted flowers on a red background. The other fittings are made of turned horn. The objective lens and the screw-on eyepiece cap are now missing.
Early telescope lenses suffered from the appearance of coloured fringes, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long - the stop lines drawn onto the draw tubes of this telescope indicate an optimum working length of about 918 mm.
Early telescope lenses suffered from the appearance of coloured fringes, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long - the stop lines drawn onto the draw tubes of this telescope indicate an optimum working length of about 918 mm.
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Object Details
ID: | NAV1495 |
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Collection: | Astronomical and navigational instruments |
Type: | Portable telescope |
Display location: | Not on display |
Creator: | Unknown |
Date made: | circa 1750 |
Credit: | National Maritime Museum, Greenwich, London, Caird Collection |
Measurements: | Overall: 320 mm; Diameter: 35 mm |
Parts: | Portable telescope |