siderostat

• POS: Noun
• HYPHEN: sid=er=o=stat

CIDE DICTIONARY

siderostat, n. [L. sidus, sideris, a star + Gr. standing, fixed, fr. to place.].

 An apparatus consisting essentially of a mirror moved by clockwork so as to throw the rays of the sun or a star in a fixed direction; -- a more general term for heliostat.  [1913 Webster]

OXFORD DICTIONARY

siderostat, n. an instrument used for keeping the image of a celestial body in a fixed position.

Etymology

L sidus sideris star, after heliostat