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coelostat

American  
[see-luh-stat] / ˈsi ləˌstæt /

noun

Astronomy.

  1. an apparatus consisting of a mirror driven by clockwork, used to enable a fixed telescope to keep the same area of sky in its field of view by compensating for the apparent rotation of the celestial sphere.

coelostat British  
/ ˈsiːləˌstæt /

noun

  1. an astronomical instrument consisting of a plane mirror mounted parallel to the earth's axis and rotated about this axis once every two days so that light from a celestial body, esp the sun, is reflected onto a second mirror, which reflects the beam into a telescope Compare siderostat

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of coelostat

1895–1900; coelo- (for Latin caeli-, combining form of caelum sky) + -stat

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.