Optically Centering A Scope?


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BullitHolz
March 24, 2009, 06:22 PM
From what I seem to understand it's best if the cross hairs are "optcally centered" in a scope for best performance. The question is...if you buy a used scope that was installed on another rifle, an you know it's been adjusted, how do you get it back to optical center?

Is there a correct way to do this or does it even matter in the first place?

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Jim Watson
March 24, 2009, 06:25 PM
Plan A - Count. Turn the windage all the way right. Turn the windage all the way left, counting clicks or graduations. Go back half way to center the windage. Repeat on elevation.

Plan B - Look. Lay the scope tube in V blocks and aim at a distant object. Twiddle the adjustments until you can roll the tube in the V blocks without moving the crosshairs off the object.

rcmodel
March 24, 2009, 06:27 PM
Most scopes, you can screw the W & E dials out all the way until they stop.

Then screw them back in till they stop again while counting the clicks.

Then screw them back out half that amount.

But when you put it on a rifle and sight it in, it's just going to be off again, unless you have adjustable mounts, so why bother.

rc

woof
March 24, 2009, 06:32 PM
I guess the only reason it matters is to make sure that an adjustment isn't so far to one extreme that when you try to sight in you don't have enough room in one direction to make the adjustments you need to make. So it doesn't have to be centered just kinda in the center.

jmr40
March 24, 2009, 06:45 PM
Unless you are using windage adjustable rings and bases it does not matter. You still have to zero the scope for your rifle. The only reason to use windage adjustable mounts is if the holes for your bases are not drilled straight.

dagger dog
March 24, 2009, 06:54 PM
Get a cardboard box that is small enough for the scope to set with the objective and ocular bells over the edge, cut two V's to acomodate the tube ,look through the scope as you rotate it , turn the windage and elevation screws to center the cross hairs in the rotating tube. Any adjustment that is close to the limits will be readily observed. Once the cross hairs are concentric in the tube then you can install it oon the rifle and be confident it is centered limit wise.

geologist
March 24, 2009, 06:55 PM
I just sight mine in on a REALLY big piece of paper.

ClayinAR
March 24, 2009, 08:15 PM
A cigar box works good.

lipadj46
March 24, 2009, 09:09 PM
Are you speaking of when after a scope is sighted in you usually "zero" the turrets? If this is what you speak then you can just sight in the new scope on the new rifle the re-zero the turrets.

BullitHolz
March 24, 2009, 10:37 PM
Actually I was thinking about a what to do with a used scope that had been mounted originally on someone elses rifle(s). A scope like that could have been zeroed and possibly re-zeroed many times over the years, throwing it WAY off optical center. It would seem to me that centering up a scope like that would be a good idea for base lining purposes before attempting to zero it on one of my rifles.

To everyone else, thanks, I love the cigar box idea!

lipadj46
March 24, 2009, 10:49 PM
I have never optically centered a scope. So from what I gather you center the reticle with the turrets then when mounted on the rifle you have to zero it using an adjustable mount or rings? Because once you mount it and start twisting turrets to zero then doesn't that get it out of center?

dakotasin
March 24, 2009, 11:22 PM
get a mirror, stand scope on mirror so you can look thru eyepiece. twist knobs until ghost image and reticle are in alignment.

it is an interesting excercise, but very few rifles are built to the level of precision needed to take advantage of it. of those few rifles, a tiny number of them will have ammo crafted to shoot up to the rifle's precision... in short, it is an interesting exercise, but you may find it is not worth your time.

good luck!

Mosin Shooter
March 24, 2009, 11:38 PM
I just sight mine in on a REALLY big piece of paper.

Old Christmas wraping paper turned backwards works great for this.
Just put a 1" dot in the center of the paper.
Then walk the scope in taking 3 shots then adjust, 3 shots adjust.

lipadj46
March 24, 2009, 11:49 PM
Old Christmas wraping paper turned backwards works great for this. Just put a 1" dot in the center of the paper.
Then walk the scope in taking 3 shots then adjust, 3 shots adjust.

They are not talking about zeroing a scope I don't think.

Dr. Tad Hussein Winslow
March 25, 2009, 12:17 AM
Mr. Watson described two ways to find the center points. Good advice indeed to accomplish that end.

But..... so you get the to the center points - so what? How does that help? When installed on the new rifle, you still have to go this way or that way to zero for the new rifle.

From what I seem to understand it's best if the cross hairs are "optcally centered" in a scope for best performance.

If they're "optically centered" as (I think) you are describing, but they're way off zero, how is that good "performance"?

Or do you mean, finding the center, and then going through base & ring combo after base & ring combo until you find one that is zeroed (or nearly so) without making any adjustments, OR strictly using base / ring adjustments until you're real close? The latter is fine on windage, I suppose - no harm - and I've done just that with crappy rings like Millett angle loc, but you're better off to just use good, solid non-adjustable rings made for the rifle, which gets you on. Then if the scope is also high quality, you WILL be close. The procedure is unnecessary with good scope and good rings. If you're using those gawd-awful Millett angle-locs, then please do yourself and all of us a favor, and ditch them, and never buy or speak of them ever again. :p

Zak Smith
March 25, 2009, 12:31 AM
Like Dr.THW said, unless you're going to change your mounts/rings/bases to "center" the reticle, it's a moot point.

atblis
March 25, 2009, 12:44 AM
Just bore sight the thing.

Jim Watson
March 25, 2009, 01:04 AM
Wish I had had Burris Signatures and some offset inserts when I had that crooked Rem 700, a good many years ago. Zeroing took up almost all the scope's adjustments and I bet the quality of scope I could afford back then was affected by shooting through the edge of the optics.

At least if you start out with your scope centered, you will know how bad off you are by the time you get on target.

sarduy
March 25, 2009, 01:36 AM
Plan A - Count. Turn the windage all the way right. Turn the windage all the way left, counting clicks or graduations. Go back half way to center the windage. Repeat on elevation.

+1

just do that

benzy2
March 25, 2009, 02:39 AM
There is often a difference in optical center and mechanical center. The spinning of the scope allows you to find the optical center. It is supposed to be the best image you will get out of the scope. The mechanical center may be the same or not depending on the scope. Thats why you wouldn't want to just center it in the mechanical range. As said it only is useful if you have windage adjustable rings/bases.

plinky
March 25, 2009, 07:45 AM
At least if you start out with your scope centered, you will know how bad off you are by the time you get on target.

Yep, and if you're too far off center you can take steps...shim scope bases, new scope mounts, new rifle.

I've not noticed a decline in optical quality at the limits of adjustment but it may be there. A problem that does exist is that your adjustments will not be true. An elevation adjustment will also move your windage and vice versa. This is a real problem for some and a frustration any time you have to change your zero.

interlock
March 25, 2009, 08:23 AM
I don't do this either.

i put the scope on and boresight then zero

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