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An optical device, such as a pair of field glasses or opera glasses, designed for simultaneous use by both eyes and consisting of two small telescopes joined with a single focusing device.

Double Telescope Binocular

An optical device, such as a pair of field glasses or opera glasses, designed for simultaneous use by…

Binoculars, or Prism Field Glasses, from Kodak in 1907.

Binoculars

Binoculars, or Prism Field Glasses, from Kodak in 1907.

Field glasses or binoculars from Ecker in Lucerne, Switzerland.

Swiss Binoculars

Field glasses or binoculars from Ecker in Lucerne, Switzerland.

Double Porro prism systems are used in small optical telescopes to re-orient an inverted image, and especially in many binoculars where they both erect the image and provide a longer, folded distance between the objective lenses and the eyepieces.

Porro Prism

Double Porro prism systems are used in small optical telescopes to re-orient an inverted image, and…

Prismatic Field Glass

Man and children on deck with binoculars.

Ship voyage

Man and children on deck with binoculars.