Heliostat
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
A heliostat throws sunlight where it might be used for photography or scientific observations. This example (half of a two-mirror instrument) has a silvered-glass octagonal mirror, clockwork mechanism, and tripod base with leveling screws. The “J. A. Brashear, Allegheny, Pa. 10” inscription refers to John A. Brashear, a sell-taught optician who, with financial backing from William Thaw, a local philanthropist, could quit his job in a steel mill and devote his energies to making telescopes and related scientific apparatus. In 1886, again with help from Thaw, Brashear established an instrument shop in Allegheny, then a suburb of Pittsburgh.
National Museum of American History’s own description
