Longland, William, 1690 c.
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photo - whole telescope
Basic Info

Maker: Longland, William

Year: 1690 c.

Year Range: 1674-1722

Year Notes: Will Longland, fl. 1674-1722

Manufacturing Location: London, England


Signature Notes:


No stand present.

Collection: National Maritime Museum

Accession #: NAV1587


Royal Museums Greenwich. "Hand-held telescope". http://collections.rmg.co.uk/collections/objects/43799.html. [Accessed: June 2016].

Public Notes:

Museum Description:
"The barrel and six draw tubes of this non-achromatic telescope are made of vellum with fittings of lignum vitae, including a screw-on cap for the objective lens. The barrel is also decorated with gold-tooled motifs and has the maker's name stamped on it: 'MADE BY WILL LONGLAND AT THE SHIP IN CORNHILL LONDON'. Early telescope lenses suffered from the appearance of coloured fringes, a problem that could be reduced by using lenses with long focal lengths. This meant, however, that the telescopes had to be very long - this telescope can be extended to over 1.5m. To make them compact and light enough to carry, they were made of several draw tubes, which were typically of papier-mâché covered in vellum. This example has a black line on each draw tube to indicate its optimum working length" (Royal Museums Greenwich).

Objective Notes:
Field stop ca. 12.2 mm diameter at ca. 58 mm from objective lens. Held in with brass split-ring.


Caird Collection

Length (open): 1493

Length (closed): 630

F-ratio: 0.0

Exit pupil:

Object status:

Optical Basics

Objective type: singlet

Optical style terrestrial

Physical style

Functional style

Materials: vellum, lignum vitae, glass, gold tooling, pasteboard, brass

Optical/Lab Data

Drawtube data:

physical lengths in mm:
starside to extension mark:
star-side tube diameter: 60
eye-side tube diameter:
ring diameter:

Drawtube notes:

Reverse taper: objective lens is located at smaller end, with each of the 3 lenses of the eyepiece located at an end of largest diameter tubes. Instrument length is over 1.5m.

Objective Data

CA curvature (diopters): CB curvature (diopters): PD lens power (diopters): fD focal length (mm): t thickness (mm): free aperture (mm): full aperture (mm): nD refractive index: ν Abbe No.:
Lens 1 21.70 28.20