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Portable telescope
This non-achromatic telescope has a leather barrel decorated with gold-tooled motifs. There are three draw tubes made of marbled paper. The other fittings are of turned ivory, including a screw-on cap for the objective lens (the eyepiece cap is missing).
Telescopes in this period had to be quite long, since lenses with long focal lengths were used in order to minimise chromatic aberration - the appearance of coloured fringes around the object being viewed. Stop lines drawn onto the draw tubes of this telescope indicate an optimum working length of about 812 mm.
Telescopes in this period had to be quite long, since lenses with long focal lengths were used in order to minimise chromatic aberration - the appearance of coloured fringes around the object being viewed. Stop lines drawn onto the draw tubes of this telescope indicate an optimum working length of about 812 mm.
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Object Details
| ID: | NAV1509 |
|---|---|
| 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: 325 mm; Diameter: 48 mm |
| Parts: | Portable telescope |