Signature:
MADE BY / WILL • LONGLAND / AT • THE • SHIP • IN / CORNHILL • LONDON
Signature Notes:
Inscriptions:
No stand present.
Collection:
National Maritime Museum
Accession #:
NAV1587
Sources:
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.
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.
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.
