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Old Soldier
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Determining the magnification of an unmarked scope
Mar 7th, 2024 at 11:09pm
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I read with interest the discussion on determining the magnification of an unmarked scope by counting bricks or window blinds. While interesting neither of these methods will work where I live. There are no brick houses here, they are either log, or sheeted with plywood. Nor does anyone have window blinds. We have long heavy curtains to keep the cold out in the winter, and block the 24 hour sun shine in the summer. So I was forced to come up with an alternate method.
    Have the wife move down to the 100 yard line. She'll bitch, but will do it if you tell her it is important. Ask her to turn around,"so the laser won't hurt your eyes" If her A.s fits within the field of view, it is a 4 power scope. Half an A.s 8 powder. Half of a butt cheek 16. If you can read the size tag, not only are her sweat pants on inside out, but you Sir have a 20 power scope. Your results may vary.
Good Day.
  

"White man have very strong Medicine. Shoot today maybeso kill you tomorrow." Esa-Tai Commanche warrior
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frnkeore
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Re: Determining the magnification of an unmarked scope
Reply #1 - Mar 8th, 2024 at 3:39am
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I like it but, I wouldn't put my wife out, like that. I think I'd find a much younger woman and save my wife all that work!!!

To bad I sold my 30X STS Sad
  

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DWT1885
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Re: Determining the magnification of an unmarked scope
Reply #2 - Mar 8th, 2024 at 2:04pm
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Curt, You gave me a good laugh on that one.  Dale.
  

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texasmac
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Re: Determining the magnification of an unmarked scope
Reply #3 - Mar 11th, 2024 at 3:17am
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Old Soldier,

Here's the technique I use.

Wayne
================
The technique is based on the telescope "rule of thumb" formula that the exit pupil diameter is equal to the diameter of the objective lens divided by the power.  Put another way, the power is equal to the objective lens diameter divided by the exit pupil diameter.  The objective lens diameter is very easy to measure.  The diameter of the exit pupil is the size of the image projected on the pupil of your eye when looking through the scope.  Measuring the exit pupil is a little more complicated.  But with a little work and preparation it’s not too hard.  To make a good measurement the scope must to be held steady, not rigidly mounted, but held sufficiently steady to make a measurement of a focused spot around 0.065” in diameter.

An easy way is to just lay the scope on a table.  Now align a bright light source, lamp for example, approximately 2 to 3 feet in front of the scope.  It must be in line with the scope and objective lens.  I.e., aim the scope directly at the lamp as if you were sighting it on the lamp.  If aligned properly the image of the light source should pass through the scope and form a small spot on a piece of paper held within inches of the eyepiece (ocular lens).  With the scope on the table and focused on a bright light, I taped a piece of paper on the back of a chair and slid it to within inches of the scope.  If the light source is too far away from the scope it may not supply sufficient light to illuminate the full spot or, if too bright, may flair out on the paper making it difficult to define and measure the spot edges.  Move the paper back and forth until the spot is focused to the smallest diameter.  Grab your calipers and measure the spot diameter.  Divided the diameter of the objective lens by the spot diameter and you have the approximate power of your scope.
  

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