James Gregory

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Gregorian telescopeJames Gregory's telescope design (1663) uses two concave mirrors—a primary parabolic-shaped mirror and a secondary elliptic-shaped mirror—to focus images in a short telescope tube. As indicated by the yellow rays in the figure: (1) light enters the open end of the telescope; (2) light rays travel to the primary mirror, where they are reflected and concentrated at the prime focus; (3) a secondary mirror slightly beyond the prime focus reflects and concentrates the rays near a small aperture in the primary mirror; and (4) the image is viewed through an eyepiece.

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James Gregory: Facts & Related Content

Written and fact-checked by The Information Architects of Encyclopaedia Britannica

Facts

Also Known As	James Gregorie
Born	November 1638 • Scotland
Died	October 1675 (aged 36) • Edinburgh • Scotland
Subjects Of Study	area • convergence • curve • divergence • fundamental theorem of calculus • infinite series • photometry • reflection • refraction • squaring the circle • telescope • trigonometry

Photos

Gregorian telescopeJames Gregory's telescope design (1663) uses two concave mirrors—a primary parabolic-shaped mirror and a secondary elliptic-shaped mirror—to focus images in a short telescope tube. As indicated by the yellow rays in the figure: (1) light enters the open end of the telescope; (2) light rays travel to the primary mirror, where they are reflected and concentrated at the prime focus; (3) a secondary mirror slightly beyond the prime focus reflects and concentrates the rays near a small aperture in the primary mirror; and (4) the image is viewed through an eyepiece.

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