Can someone tell me what this knob on back end of my Kahles scope is for?


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The Real Hawkeye
May 27, 2006, 09:41 AM
It's a 3-9 Variable, and I know about the variable knob, but there's another knob behind it that when you twist it, it seems to increas magnifation while blurring or focussing the reticle depending on how you adjust it. What's it's purpose?

Trying to answer my own question, looking at it carefully, I just noticed a tiny little arrow on the adjustment. This seems to correspond to the line on the main body of the scope, right next to the knob. If you line up the arrow with the white line, it is an adjustment somewhere in the middle of it's adjustment capacity. I am assuming that the manufacturer is suggesting this setting for normal use, and any other setting would be for extremes of distance, like very close or very distant. Am I on to something?

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rbernie
May 27, 2006, 11:31 AM
That's probably a parallax adjustment, aka side focus, knob. It's used to tune the scope optics to compensate for parallax at different ranges instead of having the optics preset to a single range (e.g. 100 yards).

The Real Hawkeye
May 27, 2006, 11:39 AM
That's probably a parallax adjustment, aka side focus, knob. It's used to tune the scope optics to compensate for parallax at different ranges instead of having the optics preset to a single range (e.g. 100 yards).Would you explain parallax?

hksw
May 27, 2006, 02:20 PM
Is this the 3-9X42 American? It does not have an adj. obj. IIRC. IMO, it sounds like the reticle focusing ring. Is it at the rear part of the ocular bell?

The purpose for the focsing ring in to sharpen the image of the reticle for your eyes. Note that the focus may be different for other folks who look through the same scope.

hksw
May 27, 2006, 02:47 PM
I take that back (although I'll still guess it as the reticle focus ring). I'm not entirely sure if Kahles scopes now have an AO ring at the rear ocular bell like some Tasco Sniper Scopes.

The Real Hawkeye
May 27, 2006, 03:01 PM
Yes, it is a ring at the farthest back position of the ocular bell, and it does seem to be a focus for the reticle. It also, by the way, changes magnification, but that might be the only way to alter the focus on the reticle. So is that all it is, i.e., a focus adjustment for the reticle?

Black Snowman
May 28, 2006, 03:35 AM
Changing focus will normally make slight changes in magnification since it will change the relationship of the objective lens with the others in the scope.

RecoilRob
May 28, 2006, 10:43 AM
Since nobody has given this a go, I'll take a stab at it.....

If you have a photograph and lay a thin, wire crosshair on it, the part of the pic covered by the center of the crosshair will not change as you look at it from different angles.

Raise the crosshairs off of the pic and you see that moving your viewing angle WILL change where the center point appears to be. That is the parallax effect.

Adjusting the scope for parallax means you focus the crosshairs to the same distance as the target. This makes the scope much less sensitive to eye position relative to bullet impact.

On a non-adjustable scope, when shooting at the factory set distance, you are fine....but closer or farther shooting makes it critical that your eye be exactly centered in the pupil....or else your shots will not be as accurate.

The Real Hawkeye
May 28, 2006, 11:24 AM
Thanks for the parallax explanation.

Serendipity
May 28, 2006, 06:04 PM
It's a reticle focusing ring. You focus it to your eyesight, only focusing the reticle. Don't focus while you've been staring through the scope for a while; look off, then focus immediately upon looking through the scope.

hksw
May 28, 2006, 09:09 PM
Yes, it is a ring at the farthest back position of the ocular bell,

As noted, that should be the reticle focusing ring. Are there also +/- marks on the Oc B?

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