Royal Museums Greenwich. "Non-achromatic telescope". http://collections.rmg.co.uk/collections/objects/43760.html [Accessed: June 2016].
Public Notes:
UPDATE 2016:
Very unusual, perhaps unique morphology: its equal diameter rings / ferrules are typical of early Galilean telescopes rather than multiple-lens eyepiece instruments.
Objective Notes 2016:
Focal length measured directly in collimated beam. Objective held in place by split-brass ring.
Museum Description:
"This non-achromatic telescope has a barrel made of mottled vellum with gold-tooled decoration. The three draw tubes are of plain vellum and have black stop lines drawn onto them, indicating the working length of the telescope. The turned wooden fittings include a screw-on objective lens cap. The ferrules or collars of the draw tubes were made by cutting sections from the tube that made the barrel - they are of the same diameter and the mottled pattern matches that of the barrel. This suggests that the telescope was made earlier than 1660" (Royal Museums of Greenwich).
physical lengths in mm:
starside to extension mark:
star-side tube diameter: 35.6, 32.5, 28.9, 25.8
eye-side tube diameter:
ring diameter: 35.5, 35.8, 36.1
Drawtube notes:
Common outer diameter of main tube and ferrules. These can be made to line up, so the leather was probably cut from a common cylinder (Richard Dunn). Main tube, Draws 1 and 2 have handwritten 'B' eyeside. Morphology somewhat resembles the "Reeve" Galilean telescope in the Willach collection.
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
2.90
345.00
11.20
18.70
Eyepieces
Notes:
3-lens eyepiece with focal length ca. 45 mm (220 mm from other end). 2-lens component has '3' on it, and fits inside the last draw. Ocular is located in last draw. Eye relief fitting has aperture of only 8.7 mm.
Dioptrice is made possible by the generous
support of the National Science Foundation, the National
Endowment for the Humanities, the Program in the History and
Philosophy of Science at the University of Notre Dame, and the Adler Planetarium & Astronomy Museum.
