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Educate me about a scopes diopter

Printed From: OpticsTalk by SWFA, Inc.
Category: Scopes
Forum Name: Rifle Scopes
Forum Description: Centerfire long gun scopes
Printed Date: September/23/2018 at 21:13
Software Version: Web Wiz Forums 11.10 -

Topic: Educate me about a scopes diopter
Posted By: ptf18
Subject: Educate me about a scopes diopter
Date Posted: November/02/2017 at 09:01
Fellows: I know that on some scopes the ocular piece can be rotated left or right in order to get the reticle "sharp" when you view it.(talking fixed power scope)

I have 20/30 - 20/40 vision.  Does the rotational movement "compensate" for my less than ideal vision?
If so.... what are the "limitations" on this adjustment? I suspect it is the range of the "diopter" of the ocular piece. If the ocular is marked 1,2,3,4.... would those numbers equate to 20/30...20/40...20/50..... Again I realize the ocular is used to get a "sharp" looking reticle.


Posted By: koshkin
Date Posted: November/02/2017 at 15:33
The diopter will compensate for your vision.  The range that the eyepiece compensates is usually around +/-2 diopters or similar.

There is not direct translation from the "20/40" type vision assessment to diopters, largely because the whole "20/40" is an archaic and largely idiotic way of quantifying human vision.

That having been said, if your vision is 20/40, that means you are slightly nearsighted, to the tune of a diopter or so.  20/80 is in the ballpark of two diopters off.  All other things being equal, it should take around 1 diopter on the eyepeice to compensate for that.  You just need to experiment with that a little and see where the reticle is at its sharpest.


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Posted By: ptf18
Date Posted: November/03/2017 at 21:47
koshkin.  Thank you for your reply. I "assumed" that the adjustable ocular performed as you note but wanted to be certain.

Now...for a follow up question. Again I realize that the adjustable ocular is rotated to attain a "sharp...crisp...etc" reticle.  I (we) just realize that this movement "compensates" (within limits of design) for our less than perfect eye vision.

My question is... If one had an astigmatism is it possible to address that issue with a lens that could be installed in a wear mounted frame (eye glass frame....shooters glasses)?  If so I would think a round lens would be ideal so as to allow the shooter to "fine tune" the astigmatism correction by rotating the lens slightly within the lens holder.

Not concerned about the "safety" issue of using 'shooting glasses"  for the sake of this discussion and understand it is of major importance.

Thanks for your input.

Posted By: koshkin
Date Posted: November/03/2017 at 23:12
There are prescription glasses that compensate for astigmatism. There are also contact lenses that do the same thing within limits.


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