Opera Glass
Opera glasses, also known as theater binoculars or Galilean binoculars, they 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 5x is usually desired in these circumstances in order to minimize image shake and maintain a large enough field of view. A magnification of 3x is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular lorgnettes of the nineteenth century
Source
Government Printing Office The Official Gazette of the United States Patent Office (Washington, DC: Government Printing Office, 1895)
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