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Optically centering a scope... i'm confused!

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Novusordo View Drop Down
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    Posted: December/19/2011 at 17:46
Hello everyone, I you guys can explain to me why there are so many ways to center a scope and which is best!


I have always used the bathroom mirror trick to center my scopes becuase I always thought it is quicker and easier than the good old method of counting clicks then clicking back halfway, but earlier tonight I came across an article on pyramid air gun blog that claimed the "bathroom mirror" trick is unreliable and that the best method is the "cardboard box" method.

Well I tried this new found cardboard box method fully expecting my scope to be perfectly centered becuase afterall I use the no-brainer bathroom mirror method, but I immediately noticed that while carefuly turning my scope a full roation as per instruction my scope's reticle was shifting away from the static point of aim by a ridiculous amount, so it seems that the bathroom mirror trick is afterall, unreliableShocked

At this point I really wanted my scope to be optically centered, but I did not want to go through the tedious process of blindly adjusting the turrets with the objective of eliminating reticle shift from the static point of aim, so instead I used the good old method of counting clicks then clicking back halfway.

Upon rotating the scope a full turn in the cardboard box method I was relieved to see that the scopes reticle kept bang-on target for the full rotation, so now I truly do have an optically centered scope and I'm quite frankly annoyed that I've been unaware using a method that does not work at all (atleast for my scope)Shocked


So guys, lets discuss this subject as I believe this is a vital step when it comes to scope diagnosis for people who have POI shifting issues.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Novusordo Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 17:48
EDIT: forgot to post the link to the box method for those that do not know about it http://www.pyramydair.com/blog/2005/07/how-to-optically-center-scope.html
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 17:48
I honestly just don't understand the point of centering it.  When you put it on the gun you are going to have to make adjustments anyway.  So what is the point?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote biggreen747 Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 18:11
I've never heard of those methods. Counting clicks (or turns) is pretty easy and foolproof. I center mine prior to mounting because I use Burris Signature rings and this allows me to make coarse adjustments with ring inserts and fine tune with windage and elevation adjustments. Some claim it is easier on the internals and light transmission is better with the internals centered. 
We measure it with a micrometer, mark it with a crayon, and cut it with a chainsaw.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Novusordo Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 18:37
Originally posted by supertool73 supertool73 wrote:

I honestly just don't understand the point of centering it.  When you put it on the gun you are going to have to make adjustments anyway.  So what is the point?


It's better to start off knowing you zeroed from a centered scope than one that could be skewed.

Also I've just realised that mechanically centering a scope is completely differing to optically centering a scope. Both should be done before zeroing-in.

Blimey the learning never stops when it comes to scopes Whacko
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 18:59
How so?  What does it really do for you?  If you bore sight it, it matters not at all where it is when you first put it on as you change it to where it needs to be.  Who cares if I have to move it two or three minutes vs one. 


Edited by supertool73 - December/19/2011 at 19:00
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Novusordo Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 19:08
This article http://www.snipercountry.com/Articles/MechanicalZero.asp explains mechanical zero just perfectly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 20:30
That is a pretty good article... one should at least be able to understand the requirements for a mechanical zero after reading it...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Thundey Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 21:44
Originally posted by supertool73 supertool73 wrote:

I honestly just don't understand the point of centering it.  When you put it on the gun you are going to have to make adjustments anyway.  So what is the point?


A scope will have its best optical clarity and light transmission when centered, or as close to it as possible.  It's what makes the burris sig rings such a beautiful piece of equipment.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: December/19/2011 at 22:40
I don't disagree with the optically centered part for the best performance.  But It is hard to say if that will ever happen once you mount it on the rifle.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: December/20/2011 at 09:42
air guns, long range 22lr and long range high power all have one thing in common and for the same reasons--- small changes in the tilt or rotation of the reticle have profound effect of poi downrange. the cure is  getting  a level ----not if the reticle is centered either mechanically or optically. As an example the z1000 diavari I use completely debunks any centering theories as scope use the reticle to the very edges of the visual field. the scope is always used either 11 moa of in the up directions or about 36 moa in down directions. Tilted 20 moa picatinny rails used in long range shooting willl show at least 3 mil of if centered at 100 yds. Most ballistic reticle scopes require either 100 yd or 200 yd poa=poi regardless of centering. The only thing centering tells you  is if your base alignment is out of whack with your receiver, ie holes drilled off center, using a dovetail mt. thats screwed over to far etc.
The next time your shooting your air gun -- tilt the target something like say  6-10 degress instead of worring about the scope and watch what happens at various distances  (this is the equivalent of not having your scope's horizon level)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Poodleshooter1 Quote  Post ReplyReply Direct Link To This Post Posted: December/20/2011 at 10:42
Originally posted by supertool73 supertool73 wrote:

I don't disagree with the optically centered part for the best performance.  But It is hard to say if that will ever happen once you mount it on the rifle.  

That's when you go to windage adjustable "standard" mounts or shimmed scope rings.
My dad has a Model 7 with misdrilled scope base holes. When first mounted,his 4200 Elite was so far off of center that it was fuzzy along one edge, until we centered the scope, and then used the mount adjustments only to get it as close to zeroed as possible. That puts the sweet spot of the glass right were it needs to be, and results in only minor adjustments to the scope to zero perfectly.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote supertool73 Quote  Post ReplyReply Direct Link To This Post Posted: December/20/2011 at 16:26
Problem with shimming and windage adjustable rings is there is a very good chance you set up your rings so they are not in the same plane.  So when you tighten them down you are putting a bind on your scope tube.  Which is bad, as it can cause all kinds of function problems and possibly permanently damage your scope.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote biggreen747 Quote  Post ReplyReply Direct Link To This Post Posted: December/20/2011 at 17:24
Which is why I keep going back to Burris Signature rings on my hunting rifles.
We measure it with a micrometer, mark it with a crayon, and cut it with a chainsaw.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: December/20/2011 at 17:34
hunting guns are shot very little, and little things like misdrilled holes, off center axis bore/receiver will probably get you by. J rigging by using burris is also considered a fix by some
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tt_tomson Quote  Post ReplyReply Direct Link To This Post Posted: December/22/2018 at 16:23
One neat trick for centering the scope before installation is hold it up to your Bathroom mirror on its lowest power setting. Tight up to the glass.
Look in it and you'll see two sets of cross hairs. Adjust until the two sets merge. Its now centered.
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