Binocular opera glasses, 1850-1880.
© Science Museum / Science & Society Picture Library
Known as opera glasses, these optical aids invariably utilise a pair of Galilean telescopes. They provide the user with a low magnification view by using large convex front lenses and concave ones for the eyepieces. This example, made by Chevalier of Paris, is of metal construction and is richly decorated with mother-of-pearl and colourful enamels. Binoculars of this type were popular for viewing the stage from afar when at the theatre or opera house.