Unknown, 1770 c.
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photo - whole telescope
Basic Info

Maker: Unknown

Year: 1770 c.

Year Range: -

Year Notes:

Manufacturing Location:


Signature Notes:


No stand present.

Collection: National Maritime Museum

Accession #: NAV1525


Royal Museums Greenwich. "Achromatic telescope". http://collections.rmg.co.uk/collections/objects/43737.html [Accessed: June 2016].

Public Notes:

"The telescope barrel is covered in rayskin (shagreen) that has been dyed green, while the four draw tubes are made of green vellum. Black stop lines on the draw tubes indicate the optimum working length of the telescope, which is over 1000 mm. The brass fittings include a sliding eyepiece cover and screw-on objective lens cover. This is an early example of an achromatic telescope. The achromatic lens was first developed in 1757 by the London instrument maker John Dollond (1706-61)" (Royal Museums Greenwich).

Length (open): 1048

Length (closed): 302


Exit pupil:

Object status:

Optical Basics

Objective type: N/A

Optical style

Physical style

Functional style

Materials: rayskin, vellum, brass, glass, shagreen

Optical/Lab Data

Drawtube data:

Drawtube notes:

Diameter: 47 mm

Objective Data



4 3 ± 2 ± 1 ±
5 4 ± 3 ± 2 ±