Selection of four opera or prospect glases, 1749-1773.
© Science Museum / Science & Society Picture Library
A selection of four miniature telescopes, a type of instrument that has been variously called an opera or prospect glas. These are small Galilean telescopes that provide a low magnification using a large convex front lens and a concave eyepiece lens. Small telescopes of this type were popular for viewing the stage from afar when at the theatre or opera house. They became popular as a status symbol in the 18th century and were made from a variety of materials including vellum, shagreen, lacquered ivory, horn, silver and bras.