Gregorian reflecting telescope, 1763-65.

Image number: 10324546

Gregorian reflecting telescope, 1763-65.

This reflecting telescope was made by the famous London instrument maker, James Short (1710-1768). It is one of several telescopes ordered by the Royal Society of London to be taken on expeditions to observe and time the transit of Venus in 1769. It may have been used on Captain Cook's (1728-1779) first voyage when he was sent to Tahiti to view this rare event. By timing the transit from far-flung parts of the world it was possible for the first time to determine an accurate distance to the Sun, and hence the size of the Solar System. The telescope was supplied with a heliometer, a split-lens micrometer (shown here attached to the front of the telescope) which was originally used to measure the angular size of the Sun.

Image number:
Science Museum/Science & Society Picture Library
Date taken:
20 October 2003 16:58
Image rights:
Science Museum

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