Portable telescope
The barrel of this non-achromatic telescope would originally have been much lighter and would have looked similar to the nine draw tubes. All the tubes are made of vellum and are decorated with gold-tooled motifs. The mounts for the lenses are made of lignum vitae. The eyepiece lens is missing.
The maker's name has been stamped around the barrel at the objective end: 'IOHN MARSHALL LUDGAT STREET LONDON'. John Marshall was one of London's leading opticians, who was a contemporary of Robert Hooke and worked in Ludgate Street.
Early telescope lenses suffered from the appearance of coloured fringes when viewing, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long, hence the nine draw tubes of this example that can be pulled out to a working length that could have been as much as two metres.
The maker's name has been stamped around the barrel at the objective end: 'IOHN MARSHALL LUDGAT STREET LONDON'. John Marshall was one of London's leading opticians, who was a contemporary of Robert Hooke and worked in Ludgate Street.
Early telescope lenses suffered from the appearance of coloured fringes when viewing, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long, hence the nine draw tubes of this example that can be pulled out to a working length that could have been as much as two metres.
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Object Details
ID: | NAV1615 |
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Collection: | Astronomical and navigational instruments |
Type: | Portable telescope |
Display location: | Not on display |
Creator: | Marshall, John |
Date made: | circa 1700 |
Credit: | National Maritime Museum, Greenwich, London. Caird Fund. |
Measurements: | Length: 574 mm (closed); Diameter: 81 mm (barrel) |