Scrabble?! HELIOSTATS

Definitions of HELIOSTATS in various dictionaries:

A heliostat (from helios, the Greek word for sun, and stat, as in stationary) is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space. To do this, the reflective surface of the mirror is kept perpendicular to the bisector of the angle between the directions of the sun and the target as seen from the mirror. In almost every case, the target is stationary relative to the heliostat, so the light is reflected in a fixed direction. According to contemporary sources the heliostata, as it was called at first, was invented by Willem 's Gravesande (1688-1742). Other contenders are Giovanni Alfonso Borelli (1608-1679) and Daniel Gabriel Fahrenheit (1686-1736).Nowadays, most heliostats are used for daylighting or for the production of concentrated solar power, usually to gen