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Eyglass "Lookover" @ Lower Powers, Why?

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Category: Scopes
Forum Name: Rifle Scopes
Forum Description: Centerfire long gun scopes
URL: http://www.opticstalk.com/forum_posts.asp?TID=20328
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Topic: Eyglass "Lookover" @ Lower Powers, Why?
Posted By: lewwetzel
Subject: Eyglass "Lookover" @ Lower Powers, Why?
Date Posted: November/12/2009 at 20:34
With AO scopes, regardless of magnificationand parallax adj. selected and at all ranges, I can look through my corrective lenses and the scope, no problem. With, say, a non-AO 3-9X or less I have to look through the scope without glasses or image is blurry. Anybody know why?  



Replies:
Posted By: 8shots
Date Posted: November/13/2009 at 01:54
I can only suggest it is because with an adjustable objective the image is precisely focused on the focal point you manually focused it on, taking your corrective lenses into account. A non AO scope is only precisely focused at one point, being the focal point that the scope lenses are designed for.
I think that this non-AO focal point is determined for normal eyes and do not take corrective lenses into account???
An AO scope also has a very short focal point, whereas a non AO scope has a longer focal point, meaning the non AO will appear "in focus" at different distances. It is thus more forgiving for improper focal point adjustment. 
It would be interesting to see if you let some-one else without corrective lenses focus the AO scope at a target and then you, without adjusting the focus, see if it is also in focus for you when you look at the same target, wearing your corrective lenses.



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