Opera glasses, also known as
theater binoculars or
Galilean binoculars, are compact, low-power optical magnification devices, usually used at performance events, whose name is derived from traditional use at
opera performances. Magnification power below 5× is usually desired in these circumstances in order to minimize image shake and maintain a large enough
field of view. A magnification of 3× is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular
lorgnettes of the 19th century.