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Another Noob question

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2015 at 14:34
Dawgdad View Drop Down
Optics GrassHopper
Optics GrassHopper
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Joined: July/10/2006
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It has been a long time since I did any optics in physics but I recall that there is more distortion at the edges of a lens than in the middle.  So, my question is....

When a scope maker sets up the reticle in the erector. Do they set the reticle to be centered in the middle of the lens system at the middle of the elevation adjustment range or at some point lower so you will have more elevation adjustment through the optical center?  For example - If the scope has 100 MOA of elevation adjustment is the reticle centered in the optical axis at 50 MOA up from dead bottom?

I assume this is why people use 20 MOA bases to be able to run the reticle up to center of optical center of lens. Seems to waste a lot of good elevation adjustment but most people don't put much more than 20 MOA difference in a scope anyway.



Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2015 at 16:34
Dawgdad View Drop Down
Optics GrassHopper
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An addendum to the question....


Windage correction full value for discussion's sake is 100 MOA full left to full right when the reticle and erector are centered. Concentric circles if you will.

IF.. your elevation setting is not in the center of the optical axis when you zero the rifle...i.e. 2 moa up from dead bottom.. Will you lose actual windage adjustment range as the length of the chord across the circle is smaller the less concentric the circles of the erector tubes? When the inner tube contacts the outer tube you have less clicks than when the tubes are concentric? Visa versa if your mount is crooked and you need to put a bunch of windage on to get it zeroed you will lose elevation adjustment too?


Combining the two questions - Are you compromising the clarity of the image, inducing more parallax error and limiting the adjustment range of your sighting system if you do not zero the rifle at the center of the optical system?


Maybe I should stick to iron sights... a lot less to worry about and I still shoot Master class scores.Big Grin

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: November/11/2015 at 17:55
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Optics Jedi Knight
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It looks to me that you have it all down pat. The maximum correction is only when zero is at the center of the scope.  The further up or down from optical center the less correction there is available.
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