siderostat

siderostat

[sid-er-uh-stat]
noun
a telescopic device for reflecting the light of a star in a constant direction, the chief component of which is a plane mirror turned by a clock mechanism to correct for the rotation of the earth.

Origin:
1875–80; sidero-2 + -stat

siderostatic, adjective
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siderostat (ˈsaɪdərəʊˌstæt)
 
n
See also heliostat Compare coelostat an astronomical instrument consisting essentially of a plane mirror driven about two axes so that light from a celestial body, esp the sun, is reflected along a constant direction for a long period of time
 
[C19: from sidero-, from Latin sidus a star + -stat, on the model of heliostat]
 
sidero'static
 
adj

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Encyclopedia Britannica
Encyclopedia

siderostat

any of a class of astronomical instruments consisting of a flat mirror that is turned slowly by a motor to reflect a given region of the sky continuously into a fixed telescope. In the traditional siderostat, the mirror is rotated by a lever arm connected to a motor that turns at a rate of one revolution every 24 hours. This so-called Foucault siderostat provides a fixed but rotating image. In recent years the Foucault siderostat has been largely supplanted by the heliostat (q.v.), which is a polar siderostat, and by the coelostat (q.v.).

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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