Cock, Christopher [attrib], 1680 c.
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photo - whole telescope
Basic Info

Maker: Cock, Christopher [attrib]

Year: 1680 c.

Year Range: 1660-1697

Year Notes:

Manufacturing Location: London, England


Signature Notes:


No stand present.

Collection: National Maritime Museum

Accession #: NAV1543


Royal Museums Greenwich. "HAnd- held telescope". [Accessed: June 2016].

Public Notes:

Not signed or dated. Attributed to Christopher Cock, the basis for the suggested dating.

"The barrel of this non-achromatic telescope is made of hand-coloured vellum, decorated with gold-tooled motifs. Each of the seven draw tubes is also decorated with gold tooling. The eyepiece and objective lenses are mounted in lignum vitae and each has a sliding brass cover. The style and workmanship, in particular the gold tooling on the barrel, suggest that it was made by Christopher Cock, a telescope maker working in Long Acre, London, in the late 17th century. He made telescopes, microscopes and other instruments for clients who included Robert Hooke, John Flamsteed and Isaac Newton. Like many early telescopes, this example can be extended to a great length. This was to allow the use of lenses with long focal lengths in order to reduce the problem of chromatic aberration - the appearance of coloured fringes around the object viewed. Black rings on each draw tube indicate an optimum length in use of almost 1.7m" (Royal Museums Greenwich).

Objective Notes:
Objective glass is surprisingly thick.

Eyepiece Notes:
3-lens eyepiece unit, lenses equally spaced.

Length (open): 1700

Length (closed): 574


Exit pupil:

Object status:

Optical Basics

Objective type: singlet

Optical style terrestrial

Physical style

Functional style

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

Optical/Lab Data

Drawtube data:

Drawtube notes:

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 6.10 45.90 31.50



652 ± 0.62 ± 0.25 ±
575 ± 0 ± ±
482 ± -0.19 ± 0.40 ±