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Do all AO bell adjusters cause reticle wandering? |
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calinb
Optics GrassHopper Joined: May/30/2010 Status: Offline Points: 36 |
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Speaking of E/W knobs, my Panorama EV has much more mushy clicks than my significantly less expensive Sport HD and Panorama EV knobs have more slop, hysteresis, and elevation/windage "coupling" too. Using my Leupold Zero-Point, I've learned that, in order to keep elevation and windage knob changes from significantly affecting one another, I must always finish adjustments by turning the elevation knob in the POI down direction (clockwise) and turning the windage knob in the POI right direction (counter-clockwise). This is sort of expected for the elevation knob, because POI down should be a tightening adjustment on the erector spring. However, right POI normally loosens the windage erector spring, as I recall. Whatever the reason, it's important for me to make the final change in these directions with the Panorama EV or I'll end up with either shift of the orthogonal adjustment, or there will be an unexpected shift the very next time I move the orthogonal adjuster. Again, these errors can be on the order of 1-2 MOA. Also keep in mind that both of my Hawke scopes have been back to the factory and found to be perfectly within specs. However, the graphs that Hawke included with the scopes on their return didn't even remotely correlate to their textual report and description of the test results. I must therefore completely disregard Hawke's findings. If Hawke personnel can't read their own simple graphs correctly, they surely can't be relied upon to conduct a test of their products either. All in all, don't count on Hawke scopes to offer better quality than any other Chinese scope. The Panorama EV does have wonderful glass in it, (noticeably better than the Sport HD), but great glass doesn't seem to be all that rare in cheap Chinese scopes. Sound mechanical design and build quality is what's rare and I'll take mediocre glass (which isn't all that bad these days) with sound and reliable mechanical design and adjusters over great great glass with a shifting reticle! |
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calinb
Optics GrassHopper Joined: May/30/2010 Status: Offline Points: 36 |
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calinb
Optics GrassHopper Joined: May/30/2010 Status: Offline Points: 36 |
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I've now completed sufficient research and measurement that I can answer my own question. The answer is not all, (but nearly all scopes) do suffer from significant error (greater than one click of their E/V dials) when their parallax settings are moved over a significant range of their adjustment travel.
I tested over two dozen scopes at SHOT, using my "optics lab in a pocket" (my Leupold Zero-Point) and some mounting hardware I made to test scopes not mounted on metal-barrel guns. Despite testing all the high-end offerings except Swarovski, I found no detectable shift (less than 1/4 MOA) in the reticles of only a few, mostly expensive, side-adjust scopes: Hensholdt Horus Falcon Leupold Mark 4 (though two VX-III AO scopes exhibited reticle movement) Nightforce (though a second Nightforce exhibited reticle movement) Steiner Minox Nikon Prostaff 5 and from my own personal collection, a Vortex Razor. The sample size I tested from each manufacturer was generally only one, so I can't say that the above manufacturers' scopes will always test well. In fact, in the couple of cases where I did test more than one scope from a manufacturer, only one scope exhibited no discernible reticle shift. The others failed. (I can easily detect 1/4 MOA shifts with my Zero-Point.) Expensive March, Schmidt & Bender, and U.S. Optics scopes failed my test as did numerous other mid-priced scopes from Burris, Bushnell, Hawke, Hi-Lux, Sightron, and many others. They all exhibited reticle shift errors greater than the resolution provided by their E/V dials, which I consider to be a failure. In general, the side adjust focus models work better than AO (an objective that turns). With side adjust, the error is typically less than AO scope error and the error is limited to elevation, which is much easier to deal-with than errors in both elevation and windage. The erros is particularly problematic when it tracks a circular path, as it typically does with an AO adjuster (not side adjuster) scope. Elevation-only errors just get "buried" in a shooter's elevation dope. Typically, the high-end side adjust scopes exhibit about three clicks of error (MOA or 1/10 mil...Regardless, I'm just talking approximate error here) over their adjustment range. AO scopes usually perform much more poorly than side adjust scopes. One exception MIGHT be the Shepherd scope I attempted to test. I did not find any reticle shift that I could correlate and attribute to AO movement, but I was running out of time and did not have time to fully secure my test apparatus to the scope. The movement I witnessed was probably the result of the Zero-Point tilting off the optic axis and it did not exhibit the typical circular motion of AO induced error. Running out of time is also why I failed to test any Swarovski scopes, but it's probably the only scope manufacturer in 12.5 miles of SHOT isles that I failed to evaluate! I tested a friend's Leupold Vari-X III and found about 3 MOA shift from its 20 yard to infinity AO settings. This is typical performance for an AO scope. I personally own cheaper scopes that do much better than 3 MOA and some that do much worse, however. I'm not going to spend a lot of time describing all my methods or defending my findings. Take the information for what it's costing you, out of pocket. If you're interested, go find a used Zero-Point and see for yourself. (Several Leupold reps at their booth advised me to hold onto my Zero-Point, because they are unlikely to offer them again, for a couple of different reasons.) Also, you can just post some graph paper out at 50 to 100 yards and strap a rifle down in a vise on a bench. the graph paper image will not remain as clear through a scope's focus range as the image in a Zero-Point, but you should be able to verify my findings. I worked in a laser optics lab in engineering grad school many years ago. My Master's thesis was "A Microcomputer Based Controller For A Liquid Crystal Lens." The lens was a realtime adaptive lens. I know enough about test, measurement, and optics to know that I've discovered a problem in the riflescope industry! At least one manufacturer has confirmed my discovery too (Vortex). I've been in touch with Vortex support staff via email and I also discussed with with the tech support person involved in my technical support "ticket" at SHOT. My experience with Vortex's response to this issue just confirms what I already knew about the company. Vortex is a very honest company offering unsurpassed customer support!
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Kickboxer
MODERATOR Moderator Joined: February/13/2008 Status: Offline Points: 23679 |
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This is an Xotic (I was obligated to destroy it… great scope, but I promised to destroy it) with 458 Lott at a few steps under 200 yards: |
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Opinion,untempered by fact,is ignorance.
There are some who do not fear death... for they are more afraid of not really living |
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calinb
Optics GrassHopper Joined: May/30/2010 Status: Offline Points: 36 |
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Nice! Guess I'm on the hook for photographic proof of my RWS scope destruction now! ;) I don't have a 458 Lott, but I should be able to hit my scope with my 50 cal. Beowulf AR at 200 yards or my 480 Ruger at much reduced range with its iron sights.
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