Rifle Scopes Using Mirror for Optical Centering?

[ShtrRdy]

I read somewhere once that a person could check the optical center of a scope by placing the Objective end of the scope against a mirror and see a reflection of the crosshair. The person could then adjust the windage and elevation to superimpose the reflected crosshair on the actual crosshair to obtain the optical center.

Does anyone know if this is a valid way to optically center a scope?

I've viewed the USOptics video of centering a scope by rotating it in the rings. I havn't tried that approach yet.

 

[Rhys]

Re: Using Mirror for Optical Centering?

The mirror method has worked well for me in the past. I ascualy have one that I keep at the bench just for that. Just remoe any sun shade, had a decent strong light behind you, and turn the power way down to be able to see better.

 

[Quarter Horse]

Re: Using Mirror for Optical Centering?

I had a problem with a Vortex scope. In talking to someone from their repair shop, the mirror method was recommended.

 

[nexusfire]

Re: Using Mirror for Optical Centering?

I don't really follow how this works?

 

[mobius38]

Re: Using Mirror for Optical Centering?

I am confused as well.

 

[FCS]

Re: Using Mirror for Optical Centering?

Problem I see with using a mirror is that the refective surface is on back side of the glass. Very common for the two surfaces to not be parallel.
If using a first surface mirror then this does not apply, though you will want to be very careful as the silver or aluminum coating will easily be scratched. Even the coated versions are pretty easily scratched up.

You'll also want to watch out for parallax error. If your eye is not centered over scope you can get an optical misalignment that aligns reflection to reticle.

Error induced by second surface mirror will probably be small enough to not matter for "roughly" centering scope optically.

Rotating scope would be more mechanical then optical IMHO.

 

[Rhys]

Re: Using Mirror for Optical Centering?

The minor amount of possible error you are refering to that could possibly be caused due to refraction through the glass falls into the category of

"picking the fly shit out of the pepper"

It is just used to give a decent starting point, and is really only an issue if your rings are adjustable for windage. Otherwise your reticle is going to end up where it ends up once you have it sighted in anyway.

 

[bigwheeler]

Re: Using Mirror for Optical Centering?

I have a konus middle of the line scope, it's optical center is almost off the right lower side of the bell. There is some junk out there. It does work , it does hold zero
and is very clear. Just don't touch that dial.

 

[FCS]

Re: Using Mirror for Optical Centering?

Not refraction. Angular misalignment due to two surfaces not being parallel.

Like I said, good enough for rough centering.

 

[223man]

Re: Using Mirror for Optical Centering?

I'm not sure I understand how exactly you do this and more importantly why. Can some one please elaborate?

 

[LoneWolfUSMC]

Re: Using Mirror for Optical Centering?

I am more concerned with aligning the optic to the line of the bore.

Rarely are you going to have the perfect setup where everything is straight. Holes have tolerances. Bases and rings have tolerances. Tolerances add up.

As long as I am only dialing a couple clicks off of mechanical zero on a high end scope then I am pretty happy. If I am putting a couple mils of windage on for a 100 yard zero, then we need to identify where the problem is.

 

[ShtrRdy]

Re: Using Mirror for Optical Centering?

Aside from wanting to hear from the experience of the membership, I wanted to adjust a used scope to a close optical zero before mounting on a rifle that has the rear ring windage adjustment, (i.e. old Redfield base and rings). I would like to use the coarse adjustment on the base to reduce the amount of windage I need to dial into the scope after mounting.

 

[M40_A1]

Re: Using Mirror for Optical Centering?

I've never heard of the mirror method before. I'll have to try it out. I can see how it would be a handy method for when the scope is already mounted.

I have always just used a small wood box with "V" notches, but this only works when the scope is not mounted. The scope tube rests in the "V" notches and the crosshairs are centered on a target. Then the scope is rotated without moving the box, the crosshairs are watched to see how much of a circular movement they make from the center of the target. Adjusting the knobs can bring you to center so the crosshairs stay centered on the target while rotating the scope.

You can also just center windage by using a vertical line on the target and adjusting so the vertical crosshair coincides with the line on the target when the scope is rotated 180-degrees.

 

[Guest]

Re: Using Mirror for Optical Centering?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ShtrRdy</div><div class="ubbcode-body">I read somewhere once that a person could check the optical center of a scope by placing the Objective end of the scope against a mirror and see a reflection of the crosshair. The person could then adjust the windage and elevation to superimpose the reflected crosshair on the actual crosshair to obtain the optical center.

Does anyone know if this is a valid way to optically center a scope?

I've viewed the USOptics video of centering a scope by rotating it in the rings. I havn't tried that approach yet. </div></div>


Using a mirror works, pure an simple. Way faster than a vee set up.

Place the objective flat onto a well lit mirror, you will see two sets of crosshairs. Ajust both the windage an elevation until you only see one crosshair, it will be close enough for government work.
Who cares if it's not perfectly, optical centered? It's fixing to be moved anyway unless you have a Gantry base.

 

[LoneWolfUSMC]

Re: Using Mirror for Optical Centering?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ShtrRdy</div><div class="ubbcode-body">I would like to use the coarse adjustment on the base to reduce the amount of windage I need to dial into the scope after mounting. </div></div>

Then worry about the mechanical center of the windage turret.

 

[jtv3062]

Re: Using Mirror for Optical Centering?

The mirror method is was easy.

 

[223man]

Re: Using Mirror for Optical Centering?

I messed around with this for the first time, pretty cool. Then I came up with a question. Would this be a viable method to test tracking? I mean if you find the optical center and zero out your turrets then dial up, down, left, and right as far as you can and then come back to "zero" you should come back to optical center, right?

 

[Guest]

Re: Using Mirror for Optical Centering?

Yes an no. In reality, unless you have a very good quality mirror, place the scope in the same place every time, have the same exact lighting, ect you will be off.

A weighted vee box, that the scope is lock into, works very will for checking the tracking.

 

[223man]

Re: Using Mirror for Optical Centering?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Gunfighter14e2</div><div class="ubbcode-body">Yes an no. In reality, unless you have a very good quality mirror, place the scope in the same place every time, have the same exact lighting, ect you will be off.

A weighted vee box, that the scope is lock into, works very will for checking the tracking. </div></div>

How off are you talking? I can under stand a little, but say I do the test and then I see that my zero is of by like 2 mils. Or could I expect to see that in the mirror?

 

[Guest]

Re: Using Mirror for Optical Centering?

When doing a tracking test, I'm looking at every step the scope has to offer, as well as every subtention the reticle has to offer as well.

You need to know what every click is, or is not, and if same is what the knob is reading. Being off by as little as a 1/10 mil, 1/4 moa, or 1/4 IPHY is not a big deal,...depending distance an target. I doubt you can define that every time in a mirror, besides when you dial up, what ever. Also how do you know that what you dialed is, where the reticle is pointed?
The whole point is to find out if the reticle is pointed where it's supposed to be, for what you have dialed in. Not just to see if it moves an returns back were you started.
A mirror is good for quickly centering a reticle, nothing more.

 

[1911pimp]

Re: Using Mirror for Optical Centering?

This is the method that Leupold uses to center the recticle it work very well

 

[hayboy]

Re: Using Mirror for Optical Centering?

In that world of new scopes that SHOULD come with reticle centered you would be good to go to zero in. Buying a used scope maybe with the windage or elevation screwed all the way to the up or left or right, the mirror works great for me to get to the center of things for a starting point. With the reticle centered and Burris Sig Zee rings on a good gun, you will have to make very small adj to zero, and will be looking through the center of scopes field of view-hayboy