heliostat

Circa 1750, from New Latin heliostata, from Ancient Greek ἥλιος (hḗlios, “sun”) + Latin status (“stationary”).

heliostat (plural heliostats)

1. A device that includes 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, and is almost always stationary relative to the heliostat, so the light is reflected in a fixed direction.
   • 2024, Jasper Fforde, Red Side Story, Hodder & Stoughton, page 90:

     In reply, the clockwork heliostats that had tracked the sun to reflect light into the indoor areas during the day now swivelled towards the street lamp to do the same for the night.

• loathiest, thiolates

Borrowed from French héliostat.

heliostat n (plural heliostate)

1. heliostat