Contradiction from Hawke USA

Jim I've always been skeptical about the mirror centering method ..Please bear in mind I am NO EXPERT !!

I have my own method that has worked well for me but don't jump in with it because So many folks regard the mirror method as Gospel !

The mirror method will get you close. But, parallax can play into this method and throw it off, slightly.

The click method will get you to zero "mechanically." But, you stand a chance of putting undue stress your scope. Also, how do we know that the glass is perfectly centered with every other part inside the scope? 

The "Spin" method is what US Optics recommends to optically zero their scopes. I explain it inhttps://www.youtube.com/watch?v=SjyoYfb7bc4&t=2s starting at the 2:20 mark. The downside to this is that you stand the chance that might possibly scratch your scope spinning it back and forth in the mounts. This shouldn't be an issue if everything is nice and clean.

Regardless of all this, the goal of finding O.Z. is to get to a center point and then click into your final setting. So, you're clicking out of O.Z. anyway. Hawke might disagree with the mirror method but, they can't possibly deny that it gets a consumer close enough to O.Z. for practical use.

Happy Shooting!

Tom

In researching these methods, I found that each one has its own benefits and uses. 

Got a mirror and want to get a quick O.Z.? Use the mirror method. 

No mirror? No way to lock the gun steady? The counting method works well here. 

Got time, a locked down rifle, and something to focus on downrange? Spin it!

Jim81

I had a similar conversation with Hawke USA about the mirror optical method. The gentleman I spoke with advised me that the mirror method, was not true optical zero, but when I pressed for more detail, he said it would get you very close. I believe he said it could be off as much as +/-3moa, but don't quote me on that exact number. Point is, it is not perfect...but will get you close. This error is due to technique and optical errors (ours, not the scopes). The spin method was best, but the mechanical would get you close as well. This pretty much supports what Tom is saying above as well.

Putting this in context, what Hawke USA wanted to accomplish with my scope issue was to determine that the scope turrets were not at the far ends of the adjustment range. Obviously if the turrets are turned to the stops or to the other end where there is no spring pressure against the erector tube, no additional adjustments of the turrets will cause predictable movement of the reticle. Hence why they usually want to start with getting the turret adjustments somewhere near the "middle" of the adjustment range to determine if the scope functions properly. Hope this helps. I will say, Tom's videos are very good and so is the support from Hawke USA.

good luck!

Jim 81, I understand the first and foremost problem is you are having inconsistencies with the shift in your POI to POA.

And I don't want to alter the narrative of his post but please help me understand the importance (if any) of Jim81's scope being "optically centered". 

Why is optically centering a scope important?

I actually did a google search on that exact term and found several explanations how to preform the task. (i.e. mirror, counting clicks end to end and dividing by two, and rotating in a "V" slot) but not very many reasons "why" and this was after reading dozens of posts on non air gun forums. 

Here is one explanation I found that kinda explained it;

"As with all optically assemblies with multiple elements (lenses, air gaps and coated surfaces) the optimal arrangement for the lease distortion, aberrations and internal reflections has all elements on a single common optical axis. However, the basis of an internally adjusted scope is to purposely tilt parts of the internal optical path to adjust the windage and elevation to align the effective axis so the POA and POI coincide." 

It reads like a design engineer on the Hubble Telescope wrote it but the last sentence made sense. That is a good "why"....... so the POA and the POI coincide. 

So, if my POA and my POI does coincide, does it really matter if:

1. My scope isn't optically centered?

2. If not, how far from optically centered is too far? (this is addressed in the original OP as explained by Hawke)

Thanks in advance, 

Dave,

Don't mean to hijack the discussion, but when I was working with Hawke USA on my scope we were trying to get the turrets "centered". This was so that we could communicate via the phone and email from a starting point of the reticle adjustments being in the center of the adjustment range. From there they will work with the customer to determine the condition of the scope and whether it needs to be sent in for replacement. In practical terms my POI (after centering the reticles) was probably 5 inches off at 30 yards, but we were able to test the scope for maintaining POI. This is not how the scope would be used in practical terms, only while testing with Hawke USA guidance.

Based on my discussion with Hawke USA they conveyed that many times the customer is complaining that the scope is not adjusting properly and that it must be defective, when in actual fact one or both of the turrets have been turned past their effective range. Once they get this step taken care of and if this fixes the issue the user will then adjust the turrets or using adjustable rings will get the POI back to POA. As I understand it there is only 1 to 1.5 full turns of the turrets till hitting the stop or actually relieving the pressure off the spring, hence why long range shooting, adjustable rings might be needed. This may not be true of all Hawke scopes but it was applicable to mine. Hope this helps?

Good info here, I have always counted clicks and then divided by two, adjust turrets accordingly and take a shot and see where POI is and go from there but I’ve also been lucky enough to get scopes that are pretty close right out of packaging, I’ll need to look up the mirror thing you are mentioning.

Here’s an article I drafted on the subject a while back.

https://www.gatewaytoairguns.org/GTA/index.php?topic=116903

Here’s an article I drafted on the subject a while back.

https://www.gatewaytoairguns.org/GTA/index.php?topic=116903

Click to expand...

Very Nice write up Reaper! sending some (+) your way! thanks for sharing.

Jim81, Have you worked it out with Hawke USA yet?

V-BLOCK!, the only way I know to truly center reticle within the scope tube, but each v-block must be cut or machined exactly the same!, and if mounted must be same on each plane, I have a set I made 20+ yrs ago (out of wood!) 

When I contacted Hawke I received the same reply about centering via the mirror method. Funny thing is that when I've taken my "new from the box" Hawke scopes "to my mirror" before doing any "turret clicking", the reticle lined up with it's reflection within a couple clicks. My Hawke scopes were optically centered before leaving the factory so it does seem that the simple "mirror method" CAN BE VALID regardless what the Hawke tech guy claims.

Anywhoo........before messing with scope turrets I check the factory optical centering via "mirror method". If the reticle lines up with it's reflection within a couple clicks the "mirror method" is also valid.

Concerning placing the objective on the mirror, the scope bell rim must be perpendicular to the centerline of the scope or the reflected reticle won't be "in the right place". I have a 3-12x44 Accushot scope with the silly built in sun shade like this..........

 

Obviously this scope can't be "mirror centered" (I couldn't even check the factory setting) so it got centered via the tedious "spin in vees". Once my scopes have been optically centered I set the turret caps so the "zero" lines up with the pointer and I use this setting as a reference just in case I need to return to "optical zero" in the future after doing some click adjustments......