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find magnification with pratical measurements (1 Viewer)

Find out binoculars' magnification with practical measurements?
I have a binoculars printed untrustful specs on it.
So lets say I am 100 meters away from a known height object, which is 3 meters high, and the view throught binoculars which is in a circle shape, is perfectly viewing a diameter of 3 meters, which means this object is just fitting in the scope's view.
And I measured the object lens are 60mm in diameter. Do I already have the magnification of this binoculars? If yes, how to calculated it?
 
. Dear powerfulforcer,
. No way do you have the magnification.

Firstly, the fact that the object lens is 60 mm in diameter has got nothing to do with the magnification or field of view or anything else really.

All you know from your example is that the real field is about one hundredth of a radian, i.e. 0.573° times three which equals 1.72° approximately.
In practical terms, it is very difficult to fit an object that exactly fills the complete field of view.
With a telescope it is easier, but with binoculars there is often a mismatch between the two barrels and also there is the parallax effect.

A simple way to find the magnification with a telescope would be to look at a regular brick wall and with one eye and using the telescope count the number of bricks that equals one brick as seen through the telescope with the other eye.
Then repeat this using the other eye without the telescope and a different eye with the telescope.
Be aware that the mortar between the bricks is also involved.

Also this is not an accurate measure, especially as the magnification varies across the field of view depending which eyepiece is used.

There are better ways of finding the magnification, which no doubt someone here will advise.

All you have done with your example is find the field of view.
The apparent field of view is approximately 1.72° times the magnification.

If you have a high quality telescope or binocular with the magnification marked then comparing the unknown telescope or binocular with a high-quality one will give you a fairly good idea of the magnification.

Hope this helps.

P.S.
another way to find the field in your example would be to use the three belt stars in Orion.
The distance between the outer stars is 2.736°.
The distance between the middle star and the outer stars is approximately 1.38° and 1.36°. You will see which is wider with a suitable telescope at about 40 times magnification maybe a bit less.
I just measured last night an MM 2 telescope and got a field size of 1.41° at 40 times with the zoom eyepiece.
 
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Find out binoculars' magnification with practical measurements?
I have a binoculars printed untrustful specs on it.
So lets say I am 100 meters away from a known height object, which is 3 meters high, and the view throught binoculars which is in a circle shape, is perfectly viewing a diameter of 3 meters, which means this object is just fitting in the scope's view.
And I measured the object lens are 60mm in diameter. Do I already have the magnification of this binoculars? If yes, how to calculated it?

Measure the objective, measure the exit pupil, and divide?
 
Thx for all of your replies.
This is the only binoculars i got.
It printed 20x-280x200 on the body and i know its must be fake after doing research on net. Dang. But its still helps me see long range stuff. Im not a birder but i do need a long range binoculars.
 
Thanks Maljunulo,
Indeed a good way, with the proviso that quite a few 60 mm binoculars are actually only 55 mm because of internal vignetting. For instance the low-priced 20×60 binoculars.
In addition, in the example above with a 3 m object filling the field of view at 100 m, the magnification is likely to be about 30 times.
If the objective lens is a full 60 mm then the exit pupil would be about 2 mm.
A 2 millimetre exit pupil is difficult to measure accurately unless one thinks about how to do it.

But thanks again.
 
. Dear powerfulforcer,
Indeed you have a wonderful binocular with 8 inch aperture or 200 mm objective lens, and the top magnification of 280 times..
Must weigh about 50 kg. You must be quite strong to handhold it.
 
Thx for all of your replies.
This is the only binoculars i got.
It printed 20x-280x200 on the body and i know its must be fake after doing research on net. Dang. But its still helps me see long range stuff. Im not a birder but i do need a long range binoculars.


Hi Powerfulforcer:

It is only a fake if the binocular DOESN'T sell and make them money!

A 280x200 would offer you less than a millimeter of exit pupil; the image would be INCREDIBLY soft and DARK! In addition the objectives would be almost 8 inches in diameter! The bino would probably weigh 60 pounds.

Some Asian firms play on the fact that most people know very little about optics and have a tendency to believe everything they read. It’s dishonest, but then . . .

Attached is a photo of a garden variety 7x50 binocular with backplates that say: “120x120”

Some people wait to take advantage of any lack of understanding they find.

Welcome to our group,

Bill
 

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