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Binoculars Explained

Rimlee Bhuyan Mar 3, 2019
Whether it is for tourism, astronomy, military, or typical outdoor use, binoculars are extensively used for a variety of purposes. It is necessary to understand how they work to make the most of them in all sorts of applications.
Many people use binoculars for watching birds and insects, or any object that is far away. A pair of binoculars is often used for watching stars and planets, and for identifying constellations in the sky.
Binoculars are optical instruments that are used for observing distant objects. They work on the same principle as a telescope, but are more portable and easy to use. The magnification of a pair of binoculars is generally fixed, and they are sometimes called field glasses. Many people own one, but very few of them know about how it works.

Working Principle

There are many different binoculars available, but the most popular ones used by amateurs are the Galilean and prism binoculars. The construction of a Binocular is like two identical telescopes, which are placed next to each other. Since these lenses are mounted side-by-side, it allows the viewer to look through it with both eyes.
Binoculars consist of two objective lenses, which are situated at each end of a pair of binoculars. The objective lens collect the light from the object that the user is looking at, and bring this collected light into focus in the eyepiece lens, which then creates a visible image that is magnified to a specified degree.
But the image, though magnified, has a serious flaw. It is upside down or inverted in nature. For a telescope, having an inverted image poses no problem, because it does not matter if the stars (or the moon) are inverted. But for watching a bird or a game through a binocular, you cannot have an inverted image.
In a binocular, corrective elements, also known as prisms, are used so that the image is right side up. These prisms are to fix this problem, and they are situated between the objective lens and the eyepiece lens.
The prisms used are nothing but cubes of glasses that act like mirrors, having no silver coating on their back. They bring the ray of light from the objective lens closer together, with the help of internal reflection. They also turn the image right side up, along with proper and correct orientation.

Magnification

When you go to a store to buy a pair of binoculars, you must have noticed some numbers etched or painted on it. This number is nothing but the magnification power of that particular binocular. This power is the number by which the image, which you can see through a pair of binoculars, is magnified.
If the power is 6, then the image is six times more magnified then the original image, which can be seen by a naked eye. The second number that is etched on it is the diameter of the objective lens. The size of the objective lens will have a bearing on the overall size of the binoculars.
Most binoculars have a fixed magnification. But zoom binoculars with adjustable magnification are also available nowadays. However, they also come with certain disadvantages. These include a narrow field of vision, low brightness and contrast, and a bulky frame. While buying it, make sure that you consider its magnification number.