Gregorian reflector

telescope

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Last updated

June 29, 2026

Quick Summary

A Gregorian telescope is a type of reflecting telescope invented by James Gregory. It uses a primary paraboloidal mirror with a hole in the center and a secondary ellipsoidal mirror. Light is reflected from the primary mirror, passes through the hole, and is then reflected by the secondary mirror to the eyepiece, producing an erect image. While this design offers an upright view, it has a limited field of view.1

Reflecting telescopes, in general, use mirrors to gather and focus light, unlike refracting telescopes that use lenses. This design avoids chromatic aberration and allows for shorter, more cost-effective tubes. Various configurations exist, including the Newtonian, Cassegrain, and Gregorian designs, each with specific mirror arrangements to achieve different optical properties.2

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Robert Hooke
…first men to build a Gregorianreflecting telescope, Hooke discovered the fifth star in the Trapezium, an asterism in the constellation Orion, in 1664 and first suggested that Jupiter rotates on its axis. His detailed sketches of Mars were used in the 19th century to
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…first men to build a Gregorianreflecting telescope, Hooke discovered the fifth star in the Trapezium, an asterism in the constellation Orion, in 1664 and first suggested that Jupiter rotates on its axis. His detailed sketches of Mars were used in the 19th century to
Read More

telescope
Reflecting telescopes
One more variety of reflector was invented by another of Newton’s contemporaries, the Scottish astronomer James Gregory. Gregory placed a concave secondary mirror outside the prime focus to reflect the light back through a hole in the primary mirror. Notable is the fact that the Gregorian design was adopted…
Read More
One more variety of reflector was invented by another of Newton’s contemporaries, the Scottish astronomer James Gregory. Gregory placed a concave secondary mirror outside the prime focus to reflect the light back through a hole in the primary mirror. Notable is the fact that the Gregorian design was adopted…
Read More