John Dollond

John Dollond (born June 10, 1707, London, Eng.—died Nov. 29/30, 1761, London) was a British maker of optical and astronomical instruments who developed an achromatic (non-colour-distorting) refracting telescope and a practical heliometer, a telescope that used a divided lens to measure the Sun’s diameter and the angles between celestial bodies.

The son of Huguenot refugees, Dollond learned the family trade of silk weaving. He became proficient in optics and astronomy and in 1752 joined his eldest son, Peter, in an optical business. In 1753 he introduced his heliometer.

In 1747 a controversy arose over Newton’s statement that chromatic aberration in lenses could not be corrected. After later experiments proved otherwise, Dollond devised an achromatic lens made of flint and crown glasses for use in telescopes. The invention earned him the Copley Medal of the Royal Society in 1758, but the prior discovery by Chester Moor Hall of England in 1729 was later recognized.