Re: Wind at 200 yards?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">Lordt;
The Adjustable Objective actually combines two semi-related adjustments, optical focus and parallax. This is a subtle but often critical difference. When the scope maker coordinates the two adjustments correctly, all is well. But this is often not done properly during scope assembly, and while focus is obvious, parallax is not.
Once you have your scope focussed as sharply as possible, wag your head up and down, side to side, while observing through the eyepiece. If the crosshairs and point of aim remain stationary with respect to each other, then parallax is correctly compensated. If, however, the crosshair appears to move with the eye across the point of aim, then the prallax is improperly compensated. It is very much possible for the relationship between parallax and focus to be out of sync with a riflescope, and this subtle difference is actually very common among lower priced optics. For as much as the crosshair moves across the POA between shots, the effects of parallax displace the POI by precisely the same amount. In order to obtain a proper parallax compensation with such scopes, it can become necessary to readjust the A/O to remove the relative motion, and consequently to also at least partially defocus the scope.
Many scopes have a fixed parallax compensation, and these scopes are arbitrarily set up to be properly compensated at one single distance. With hunting scopes this is often either 100 or 200yd.
When using a scope that is either poorly compensated or not adjustable at distances different from the arbitrary distance, one should take a moment to center the eye behind the eyepiece. This is accomplished by doing the 'head bob and wag maneuver' behind the eyepiece, and then carefully positioning the eye in the estimated center of the limits where the edge shadowing occurs. This is called 'quartering the reticle', is how one finds the proper cheek weld with a riflescope, and why it is so important.
My approach to parallax is to confirm it's presence or absence each time I shoot, and when necesssary, quarter the reticle for each shot. I personally suspect that unrecognized imcorrect parallax compensation is responsible for maybe even as much as the majority of all group dispersion, and that it is impossible to shoot to the shooter/rifle's full potential without taking it into conscious consideration for every shot. Proper linkage and synchronization of the parallax and focus combination adjustments is one of the lesser known key features that you pay the extra bucks for with more expensive optics, but one should never assume it's correct. Always do the 'maneuver'.
Greg</div></div>
Greg,
I think you said it very well. Interestingly, even for folks who do understand it, recognizing a consistent perspective of aim, to minimize the effects of parallax error, may not be as easy or as possible as it is to minimize sight alignment error using iron sights. In other words, eyeball movement off a good chipmunk stock weld will reveal perfection of sight alignment using irons, while using a scope, only gross recognition of divergent perspectives are possible. This may be why I'm not any more likely to shoot better scores using a scope than when using irons, that is of course assuming I can establish a consistent relationship between the front sight and target.
