Dollond, 1770 c.
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Photo

photo - whole telescope
Basic Info

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 #: NAV1483

Sources:

Royal Museums Greenwich. "Achromatic Telescopes". http://collections.rmg.co.uk/collections/objects/43695.html [Accessed: June 2016].

Public Notes:

"The design of this telescope, with its slightly tapering decagonal mahogany barrel, is characteristic of those 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 other fittings are brass and include a single draw tube and sliding eyepiece and objective lens covers. The objective lens is achromatic, making this quite an early example of an achromatic telescope, for which the London instrument making firm of Dollond held the patent until the 1770s. The name 'Jno. Miller HYTHE 1781' is inscribed on the draw tube and probably refers to the original owner. The maker's name is inscribed on the objective lens cover as 'DOLLOND LONDON'. A similar telescope appears in a portrait of Captain Sir Edward Vernon (1723-94), BHC3069" (Royal Museums Greenwich).

Length (open): 734

Length (closed): 660

F-ratio:

Exit pupil:

Object status:

Optical Basics

Objective type: doublet (unknown)

Optical style

Physical style polygonal

Functional style

Materials: wood, brass, glass, mahogany

Optical/Lab Data

Drawtube data:

Drawtube notes:

Diameter: 38-43 mm (barrel), 48 mm (max).

Objective Data

Eyepieces

Notes:

WavelengthParaxial70%Whole
652 ± 0.2 ± 0.3 ± ±
575 ± 0 ± ±
482 ± 2.6 ± 0.2 ± ±