Changes

'''Binoculars''' are an [[optics|optical]] aid used to view distant objects with both eyes, such as scenery, wildlife, or far off boats or ships. They can also be employed in basic [[astronomy]], in lieu of a [[telescope]].

'''Binoculars''' are an [[optics|optical]] aid used to view distant objects with both eyes, such as scenery, wildlife, or far off boats or ships. They can also be employed in basic [[astronomy]], in lieu of a [[telescope]].

They consist of twin barrels containing a system of lenses one for each eye.  Because the distance between the eyes varies from person to person, there must be provision for adjusting the distance between the binocular's eyepieces; thus the barrels are hinged together.  

They consist of twin barrels containing a system of [[lens]]es one for each eye.  Because the distance between the eyes varies from person to person, there must be provision for adjusting the distance between the binoculars' eyepieces; thus the barrels are hinged together.  

While most binoculars are simply designed to be purely functional, opera glasses are a kind of binoculars that are usually rather [[ornate]] in finish.  They are used to improve the patron's view of the action on [[stage]].  The fancy form fits in with the formal nature of a performance and the highly decorated interior of most [[theater]]s.

While most binoculars are simply designed to be purely functional, opera glasses are a kind of binoculars that are usually rather [[ornate]] in finish.  They are used to improve the patron's view of the action on [[stage]].  The fancy form fits in with the formal nature of a performance and the highly decorated interior of most [[theater]]s.

Because they are used to view terrestrial objects, the images in a pair of binoculars need to be erect, i.e. right-side-up. This poses an engineering challenge. There is a kind of telescope, the ''Galilean telescope,'' which uses only lenses and provides an erect image. Some instruments use a pair of Galilean telescopes. This design is inexpensive, can be compact, and can produce a sharp image; however, their magnification, field of view, and "exit pupil size" (which determines brightness) are all limited. This design was once popular for opera glasses, but today is found mostly in children's toy binoculars.

Because they are used to view terrestrial objects, the images in a pair of binoculars need to be erect, i.e. right-side-up. This poses an engineering challenge. There is a kind of telescope, the ''Galilean telescope,'' which uses only lenses and provides an erect image. Some instruments use a pair of Galilean telescopes. This design is inexpensive, can be compact, and can produce a sharp image; however, their magnification, field of view, and "exit pupil size" (which determines brightness) are all limited. This design was once popular for opera glasses, but today is found mostly in children's toy binoculars.

Most modern binoculars are ''prismatic binoculars.'' The lens systems used in them are similar to the design of a "astronomical" refracting telescope, but a system of erecting prisms is added to turn the image right side up.  

Most modern binoculars are ''prismatic binoculars.'' The lens systems used in them are similar to the design of a "astronomical" refracting telescope, but a system of erecting [[prism]]s is added to turn the image right side up.  

In the traditional design, the presence of a prism system is visible in a dogleg appearance of the two barrels, the eyepieces being offset and out of line with the main barrel. However, in recent decades, optics firms have developed very compact prismatic binoculars with prism systems are inline with the barrels with no visible offset.

In the traditional design, the presence of a prism system is visible in a dogleg appearance of the two barrels, the eyepieces being offset and out of line with the main barrel. However, in recent decades, optics firms have developed very compact prismatic binoculars with prism systems are inline with the barrels with no visible offset.