cœlostatn.
/ˈsiːləʊˌstat/ Astronomy.
An instrument consisting of a mirror turned by clockwork on an axis parallel to itself and to the axis of the earth, by means of which the celestial bodies may be observed and photographed as in a stationary position.
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cœlostat1898
1898 Standard 24 Jan. 4/5 The present phenomenon [sc. the total solar eclipse of January 22, 1898] will be remembered as the first in which the instrument called the cœlostat was used.
1900 H. H. Turner in Monthly Rev. Sept. 108 A special arrangement..called a ‘cœlostat’, which reduces the whole sky virtually to rest in a most convenient manner. It was invented long ago by a Frenchman, but practically forgotten.
1939 Jrnl. Brit. Interplan. Soc. 5 9 The cylindrical objects shown just above the catwalk..are coelostats. These are synchronised, motor-driven mirror devices something similar to a stroboscope, and it is by means of these that a stationary view of the heavens is provided for navigational observations while the ship is in rotation.
1961 Guardian 13 Feb. 16/3 A coelostat lent by the Mill Hill Observatory..produces a static image of the sun.
This entry has not yet been fully updated (first published 1933; most recently modified version published online June 2018).
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n.1898