DOLLOND, JOHN

born June 10, 1706, London, Eng. died Nov. 30, 1761, London British maker of optical and astronomical instruments who developed an achromatic (non-colour-distorting) refracting telescope and a practical heliometer, a telescope used 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. Two years later 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, but the prior discovery by Chester Moor Hall of England was later recognized.