Maker: Dollond

Year: 1770 c.

Year Range: -

Year Notes:

Manufacturing Location: London, England

Signature: Dollond/ London

Signature Notes:

Inscriptions:

No stand present.

Collection: National Maritime Museum

Accession #: NAV1487

Sources:

Royal Museums Greenwich. "Polygonal Telescope". http://collections.rmg.co.uk/collections/objects/43699.html [Accessed: June 2016].

Public Notes:

"The octagonal mahogany barrel, which is now damaged, is characteristic of telescopes produced in the 18th century for use on board ship. The barrel was designed for strength, since the techniques for manufacturing strong round barrels were not well developed at this time. The brass fittings include a single draw tube on which the maker’s name is inscribed as ‘Dollond, / London’. This was the firm started by the London optical instrument maker Peter Dollond (1731–1820). It was Peter's father, John Dollond (1706–61), who took out a patent for the achromatic lens in 1758. This type of lens eliminated the problem of coloured fringes caused by the distortion of light as it passed through the glass. The objective lens cap and parts of the eyepiece are now missing" (Royal Museums Greenwich).

Length (open): 770

Length (closed): 622

F-ratio:

Exit pupil:

Object status:

Objective type: triplet

Optical style

Physical style polygonal

Functional style

Materials: wood, brass, glass

Drawtube data:

Drawtube notes:

Diameter: 43 mm

Objective Data

Eyepieces

Notes: