Unknown, 1690 c.
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photo - whole telescope
Basic Info

Maker: Unknown

Year: 1690 c.

Year Range: -

Year Notes:

Manufacturing Location: England / Italy


Signature Notes:


No stand present.

Collection: National Maritime Museum

Accession #: NAV1491


Royal Museums Greenwich. "Non-Achromatic telescope" http://collections.rmg.co.uk/collections/objects/43703.html [Accessed: May 2016].

Public Notes:

Museum Description:
"The barrel and four draw tubes of this non-achromatic telescope are made of vellum. The barrel and collars of the draw tubes have a marbled background and are decorated with gold-tooled motifs. The objective lens is set in a turned wooden mount, but it appears that the screw-on lens cap is missing. The telescope is believed to be a companion to NAV1490 and may have belonged to Rev. Ralph Taylor, who went into exile with King James II (reigned 1685-88) and later lived in Rotterdam in the Netherlands" (Royal Museums Greenwich).

Possibly made in England, museum site suggests Italy.

Objective notes:

Focal length using collimated beam = 765 mm. With open length of 670 mm, negative lens focal length is thus 95 mm. This gives magnification of 765/95 = 8x.


Museum notes indicted that this telescope once possibly belonged to Rev. Ralph Taylor, a contemporary of King James II who was exiled with him (1688).

Length (open): 681

Length (closed): 213


Exit pupil:

Object status:

Optical Basics

Objective type: singlet

Optical style galilean

Physical style

Functional style

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

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 1.31 765.00



Eyepiece 1
fD focal length (mm): free aperture (mm): full aperture (mm): s spacing (mm): CA curvature (diopters): CB curvature (diopters): M magnification: FOV field of view (degrees): Thickness:
Lens 1 -95.00 8.10
652 ± -1.8 ± 0.5 ±
575 ± 0 ± ±
482 ± 4.8 ± 0.7 ±