Things you should learn before buying a binocular


Binocular is an instrument that has two identical and mirror-symmetrical,parallel placed telescopes for closer look of distant objects. A binocular is handy to many people for different purposes, like for watching celestial objects, hunting, fishing, bird watching, sports and travelling. There are different kinds of binoculars available in market and the selection of one that is suitable to serve your purpose may be quite difficult. You must have in-depth knowledge about different types of binoculars for selecting and purchasing the right one.

Know the quality

You should know how the quality is determined for binoculars. When the mechanical build of the binocular is strong and its optical ability is higher compared to others, is considered as good binocular. Price may go up with the better quality products. The quality of binocular actually depends on many things, like type of glasses used, the kind of coverage and anti-reflection facility it gives, the construction of lens barrel, the position of prisms and finally the finish of the instrument. Sometimes, the renowned brands of binoculars are the signatures for best quality, though they are much expensive. There are also some companies that make binoculars of good quality in a comparative lesser price. Be aware of the sales clerks who cannot provide proper information about the binocular you want to buy.

Types of binoculars

Two major classes of binoculars are porro prism binocular and roof prism binocular. The first one is the most commonly used and most useful for astronomical purpose. The second type is more expensive as they contain a prism to correct the image.

Following are the technical details of binoculars for complete understanding of its operative method:

Eyecups of binoculars

It is possible to adjust the eyecups in all binoculars according to the users’ requirement. Those who wear glasses can roll up the eyecups to have the wider view. These can be folded town or twisted or slide up and down for better adjustment.

Power formula

The power of the binoculars generally varies between 7 to 10, beyond which it is not permissible to increase the power. There is a formula to determine the possible enlargement of the image for a binocular of particular power. Those which have powers more than 10 need tripod for mounting to view the steady image.

Exit pupil

The ability of pupil of eyes to open in dark and contract in light diminishes with old age. So different people need to buy different types of binoculars as exit pupils vary with requirement. For example, exit pupil of 7mm is standard for astronomical watch while 6mm is sufficient for bird watching.

Eye relief

This is the term to denote how far from your eyes you can place the eyepieces but still can have the view of whole field. Normal eye relief for standard binoculars vary between 9 to 13 mm.

Types of prisms

Two major classes of prisms are BAK-4 and BK-7. The BAK-4 is required for celestial viewing and provides brighter and better view.

Lens coatings

Light might get lost after it hits every glass surface (lens or prism) and reflects back. To ensure entry of more light in the eye for sharp and precise image viewing, different types of optical coatings are applied on the glass surfaces.

Knowing the technical details is important for complete understanding of the functionality of binocular. If you can figure out which one are good binoculars, you can select the best one to serve your purpose.

It is important to understand the technical terminology and functionality of different parts of binoculars for proper selection and purchase. Only a good quality binocular can serve your particular requirement.

Author’s Bio: Kenneth Jones is a physicist and teaches astronomy in University. He is an amateur astronomic observer. Kenneth has many binoculars and telescopes in his collection. His other love is travelling in forests and watching wildlife.

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