image astronomical quadrant RS_63 pic1
Image number: RS.8471
Credit: © The Royal Society
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Astronomical quadrant


ca. 1767


John Bird (1709-1776, British), Instrument maker

Object type

Archive reference number



Content object


A 12-inch brass astronomical quadrant, comprising a piece of metal in the shape of a quarter circle and a telescope. Supported by a long neck and a four-foot base. Inscribed 'RS 62' in a number of places and 'J. Bird London' along the curved edge of the quarter circle.

Used to measure the angle of a celestial objects from the zenith, this particular design incorporated innovations to reduce observational inaccuracies, as described by Bird in his Pamphlet 'The Method of Dividing Astronomical Instruments…' (John Nourse, London, 1767). It is traditionally thought to be the quadrant used by Captain James Cook (1728-1779) during his observations of the transit of Venus in Tahiti in the 1760s.

John Bird (1709–1776) British instrument maker was not a Fellow of the Royal Society.

Object history

Exact provenance unknown. Likely commissioned by the Royal Society in their preparations for the Transit of Venus and deposited with them on the return trip to London, at some unknown date post-1769.

Associated place

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