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locking vs non locking focus?

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30mikemike View Drop Down
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    Posted: August/23/2008 at 00:11
Although they can be a pain, the ocular lens focus systems that have a locking ring (like Leupod) dont move once locked down. I have noticed on a scope with the quick focus, a schmidt & bender, that when the focus is away out (bad eyes with glasses) that the eyepice can be moved left to right, up to down a little bit and the crosshairs appear to move about 1" at 200 yards. Now it doesn't stay moved once you let it go but I wonder if that's normal or not and should I be concerned?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 00:33
Originally posted by 30mikemike 30mikemike wrote:

should I be concerned?

No.  Look again really closely--the target is moving with the reticle so even if it did stay (which of course it won't) POI wouldn't change at all.

Also, the Leupold type certainly can come loose if you don't make them "pipe wrench tight," and that makes them a PITA anytime you want to move them in the future.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 30mikemike Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 20:11
Thanks for yout advice, The reticle moves on the target, it does not maintain the same point on the target. I had a Steiner a few years ago that did the same thing. One day it was a one hole scope, the next, groups like a coach gun with 00 buck. Never used a pipe wrench on a lock ring style, a dab of blue (low strength) locktite will keep them were you want them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 21:38
First, if you know the answer why are you asking the question?

Second, how carefully are you making the observation that the reticle is moving on the target?  I ask because, unless you have a relatively rare SFP S&B, it's physically impossible to move the reticle relative to the image of the target by wiggling the focus ring unless you're shaking the entire scope.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 21:45
Originally posted by Jon A Jon A wrote:

First, if you know the answer why are you asking the question?Second, how carefully are you making the observation that the reticle is moving on the target?  I ask because, unless you have a relatively rare SFP S&B, it's physically impossible to move the reticle relative to the image of the target by wiggling the focus ring unless you're shaking the entire scope.

My NcStar does it...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 22:15
And your NcStar has what in common with a FFP S&B?  They're both black?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: August/23/2008 at 22:20
Originally posted by Jon A Jon A wrote:

And your NcStar has what in common with a FFP S&B?  They're both black?

Well, it obviously escapes you that they have at least ONE thing in common, other than being black.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote helo18 Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 00:11
Originally posted by Kickboxer Kickboxer wrote:

Originally posted by Jon A Jon A wrote:

And your NcStar has what in common with a FFP S&B?  They're both black?

Well, it obviously escapes you that they have at least ONE thing in common, other than being black.


Laugh%20Above  I just think that response is great Kickboxer!  I wouldn't think that moving the focus piece should move the reticle.  I would say there is something wrong with it.  Never had that happen on a scope before.


Edited by helo18 - August/24/2008 at 00:12
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Jon A View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 00:19
Originally posted by Kickboxer Kickboxer wrote:

Well, it obviously escapes you that they have at least ONE thing in common, other than being black.

Could you give us a brief description of the procedure you use to display this phenomenon? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 00:32
Move focus ring, RETICLE moves relative to target image... rather wildly at times. If care is exercised, the reticle can be, shall we say, "adjusted" so that accuracy and focus is maintained. However, if care is not exercised, POA and POI are not the same while the scope will be in focus. I do not know if this is common to NcStar scopes, I have never seen the effect before and it does not occur in any of the other scopes I have.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 00:35
Originally posted by helo18 helo18 wrote:



Originally posted by Kickboxer Kickboxer wrote:

Originally posted by Jon A Jon A wrote:

And your NcStar has what in common with a FFP S&B?  They're both black?

Well, it obviously escapes you that they have at least ONE thing in common, other than being black.
Laugh%20Above  I just think that response is great Kickboxer!  I wouldn't think that moving the focus piece should move the reticle.  I would say there is something wrong with it.  Never had that happen on a scope before.

I agree Helo, must be a scope problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 02:59
I agree.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 10:35
put this question up on SH-- 61 hits and not one explanation-- it would seem that theory and experience are colliding.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 30mikemike Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 10:38
Update: called S&B and they said rare but possible. Send it back and they will analyze and fix for free if necessary. To put an NC in the same room with an S&B is like saying a Pinto and GT40 are both cars!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 10:53
Originally posted by 30mikemike 30mikemike wrote:

Update: called S&B and they said rare but possible. Send it back and they will analyze and fix for free if necessary. To put an NC in the same room with an S&B is like saying a Pinto and GT40 are both cars!


Aren't they?
I don't think KB was putting his NC "in the same room" as S&B. He was just stating that he has seen this issue with his scope. Everyone here knows the Schmidt & Bender is an outstanding scope. Most also know what an NC is.

Doug
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dale Clifford Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 11:24
Probably impossible to make the statement that wobble was the only problem in either case also.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 11:38
Originally posted by Dale Clifford Dale Clifford wrote:

Probably impossible to make the statement that wobble was the only problem in either case also.


For sure and I think 30mm is on the right track. It should be sent back for inspection.
Adjusting focus has never changed POI for me, either.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gunshow75 Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 14:05
Originally posted by Dale Clifford Dale Clifford wrote:

put this question up on SH-- 61 hits and not one explanation-- it would seem that theory and experience are colliding.

Scopes have an optical axis. Lets assume that both the center of the image formed by the objective and the center of the reticle are perfectly aligned on the optical axis. Focusing the scope by adjusting the objective lens is intended to move the image along the optical axis such that image and the reticle lie in the same plane.

Imagine what would happen if the mechanical motion of the lens was such that moving the lens caused the image to move away from the optical axis. It might move left, right, up, down, or whatever, but away from instead of along the optical axis. In that event, even though the image and the reticle were in the same plane, the center of the image will not remain aligned with the center of the reticle.


Tom



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jon A Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 14:26
Originally posted by Gunshow75 Gunshow75 wrote:

Focusing the scope by adjusting the objective lens is intended to move the image along the optical axis such that image and the reticle lie in the same plane.

OK, now you're talking about an adjustable objective to eliminate parallax?  I agree this certainly could change POI if there's slop. 

But that's not what we're talking about here.


Edited by Jon A - August/24/2008 at 14:27
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 14:46
Originally posted by Jon A Jon A wrote:

Originally posted by Gunshow75 Gunshow75 wrote:

Focusing the scope by adjusting the objective lens is intended to move the image along the optical axis such that image and the reticle lie in the same plane.

OK, now you're talking about an adjustable objective to eliminate parallax?  I agree this certainly could change POI if there's slop. 

But that's not what we're talking about here.


Exactly, we are talking about focusing the ocular lens for a clearer reticle.
I certainly have seen changes, not in POI, but in my groups. Being able to put a clean, crisp reticle on the target is necessary for me.
Also, getting back to the locking ring. I never had problems with my Leupold, Burris and other locking rings in the past. Now that I wear progressive lenses I find myself adjusting the focus more often. I haven't had problems with the fast focus on Monarch, 4200 and Kahles so far. I was worried about it moving, too. A little nail polish on the ring lets me know where my sweet spot for focus is, should it move.
Once set I shouldn't have to move it but I'm still getting used to the sweet spot on these glasses. Shooting from the bench, offhand and prone changes my eye/scope relationship and is probably the problem.

Doug


Edited by tahqua - August/24/2008 at 14:59
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gunshow75 Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 15:26
You are correct and I apologize; I looked at the first sentence of the original post and read it as adjusting the objective instead of the ocular.

If a reticle is not in the same plane as the image, moving the ocular could produce the same effect.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote tahqua Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 15:51
That's easy enough to make mistakes on. We have AO's, fast focus and various side focus scopes out there. It has sent me down the wrong path before, too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gunshow75 Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 15:54
I suspect the reason I read it as an objective lens issue is because I always think of the ocular lens when I see the word focus.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gunshow75 Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 15:56
My second mistake today. I meant to say that I always think of OBJECTIVE lens when I see the word Focus.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: August/24/2008 at 20:27
Originally posted by 30mikemike 30mikemike wrote:

Update: called S&B and they said rare but possible. Send it back and they will analyze and fix for free if necessary. To put an NC in the same room with an S&B is like saying a Pinto and GT40 are both cars!

30MM, there is no comparison in almost any aspect between S&B and NcStar. NcStar is a toy, S&B is a tool. However, there are many toys and tools that have similar functions and perform in similar manners and therefore have a basis for comparison. Just because one scope is much cheaper than another does not mean that it cannot compare in MANY respects to another, more expensive, more capable piece of equipment. This carries true in all aspects of the Test and Evaluation world.
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