heliometer

noun

he·​li·​om·​e·​ter ˌhē-lē-ˈä-mə-tər 

: a visual telescope that has a divided objective designed for measuring the apparent diameter of the sun but also used for measuring angles between celestial bodies or between points on the moon

heliometric

ˌhē-lē-ō-ˈme-trik 

adjective

heliometrically

ˌhē-lē-ō-ˈme-tri-k(ə-)lē 

adverb

Word History

Etymology

French héliomètre, from hélio- heli- entry 1 + -mètre -meter

First Known Use

1753, in the meaning defined above