coelostat
noun
coe·lo·stat
plural -s
: an instrument consisting of an adjustable plane mirror clock-driven on an axis parallel to the axis of the earth and a second fixed mirror that act together to send light from a celestial body in a fixed direction compare heliostat
Word History
Etymology
International Scientific Vocabulary coelo- (from Medieval Latin caelum sky, heaven, from Latin caelum heaven) + -stat