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

Opera

Opera is an art form in which singers and musicians perform a dramatic work combining text and musical score, usually in a theatrical setting. Opera incorporates many of the elements of spoken theatre, such as acting, scenery, and costumes and sometimes includes dance...

 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

Field of view

The field of view is the extent of the observable world that is seen at any given moment....

. A magnification of 3x is normally recommended. The design of many modern opera glasses of the ornamental variety is based on the popular lorgnette

Lorgnette

A lorgnette is a pair of spectacles with a handle, used to hold them in place, rather than fitting over the ears. It is derived from the French lorgner, to take a sidelong look at, and Middle French, from lorgne, squinting. They were invented by an Englishman named George Adams. The lorgnette was...

s of the nineteenth century.

See also

• Binoculars
  Binoculars
  Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects...
  
  
• List of telescope types
• Monocular
  Monocular
  A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and sometimes prisms; the use of prisms results in a lightweight telescope. Volume and weight are less than half those of binoculars of similar optical...
  
  
• Telescope
  Telescope
  A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
  
  
• Spotting scope
  Spotting scope
  A spotting scope is a small portable telescope with added optics to present an erect image, optimized for the observation of terrestrial objects...