Signature:
Ayscough / London / Inv & Fec.” and “no 559 / 360
Signature Notes:
Inscriptions:
No stand present.
Collection:
Louwman Collection of Historic Telescopes
Accession #:
LC 49
Sources:
Louwman, P.J.K., and Zuidervaart, H.J., "A Certain Instrument to See Far: Four Centuries of Styling the Telescope Illustrated by a Selection of Treasures from the Louwman Collection of Historic Telescopes". Wassenaar, 2009. p.72. #53.
Louwman, P.J.K., and Zuidervaart, H.J., "A Certain Instrument for Seeing Far: Four Centuries of Styling the Telescope Illustrated by a Selection of Treasures from the Louwman Collection of Historic Telescopes". Wassenaar, 2013. p.79. #49.
Public Notes:
"Cylindrical wooden tube in two parts, which can be screwed together by means of threaded brass bezels. There are two objectives in a rotating mount, enabling two different magnifications.
The instrument maker James Ayscough (?-1759) was first an apprentice and later a partner of the instrument maker James Mann (1706-1756). He worked as an independent instrument maker from 1748 onwards. Ayscough’s premises were located at Ludgate Street, near St. Paul’s cathedral in London. Ayscough was a creative instrument maker, who designed many optical novelties. He was the first optician who made spectacles with foldable arms. Among Ayscough’s inventions were also the first sunglasses with green or blue coloured lenses. In 1754 Ayscough invented a changeable objective for different magnifications. (Cf. A Description of a Telescope adapted to use at Sea). The rotating objective on his telescope is a variation on that design. Another important innovation in which development Ayscough played a remarkable role, was the invention and construction of the achromatic objective: a combination of a positive crown glass lens and a negative flint glass lens. According to tradition Chester Moor Hall, an English ‘Gentlemanscholar’, invented this kind of telescope in about 1730, far before the 1756-patent of John Dollond. It is an established fact that Ayscough has constructed achromatic telescopes made according to a design that is attributed to Hall. The early Dollond-telescopes also followed this design" (Louwman and Zuidervaart, 2013).
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.
