scope parallex adjustment question

Forums Optics, Scopes, Rings, & Mounts scope parallex adjustment question

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    pete72
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    so I bought a hammers adjustable objective 3-9×32 scope. never owned one before and have done a bunch of reading from different internet sources but still have questions. first is why optically center the crosshairs when I’m gonna have to move them to zero the scope for the yardage I want to zero? I’m on paper and very close with plenty of adjustment both directions. after mounting the scope I set my objective to infinity setting and then looked into the blue sky to set my rectile focus so it was sharp and clear. now I can turn the scope power down to lets say 5  then look at my target  which is only 3/4” dot @20 yrd’s  then turn my objective lens till its clear which does not correspond with the factory marked yardages printed on the end. no worries as I’ve read there never right anyways just a ballpark figure. I’ve also read the rectile focus once set should never be touched again unless there is say a prescription change etc .  now if I were to go higher or lower with the magnification power 3-9  then the scope gets blurry. so my question is do I just use the objective lens adjustment to keep my scope clear and focused.  if someone had a accurate scope set up link pertaining to proper set up of a ao scope I would like to see it.  seems there are lots opinions as to the correct way but all are different.     

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    JohnL57
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    I am certainly no expert, but the way I understand it, when the parallax is set correctly for the distance to target, with the gun held in a rest or otherwise stabilized so it won’t move, when you bob your head side to side and up and down the crosshairs don’t move off the target.(hope that made sense!) I’ve tried this with my Hawke Varmint scope and found that when I’ve got the parallax adjusted right the target is not in focus. What I finally did was to quit worrying about it! I just set the scope so the target’s in focus and blast away. Admittedly I don’t shoot Benchrest but I have shot a few Field target matches and done pretty well. If I recall that scope is on your springer and the variations in the way you hold it will probably induce more POI shift than the scope parallax setting. When hunting with my springer I usually set the focus for the most likely distance I’m liable to get a shot (usually 15 yards) and only tweak it if the shot is way closer or further away(assuming I have time to mess with my scope!)
    Hope that helps,
    John

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    pete72
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    thanks for the reply johnL57.  seems to be lots of mystery to the parallax adjustment. i’d just like to get it set up properly and know what I have is right! I’d like to be able to have it so I can do good bench rest shooting up to  50 yards and say small game to 35 yards that way I can zero @20 and still be good @35 but at 35 and 50 I need more magnification and it seems like when I go up in power and shoot at 35 yards I’m fuzzy so I readjust the objective to clear it up but now I’m no longer zeroed and shooting off. if zeroed properly at 20yards I should also be good at 35 yards but I’m not.

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    spysir
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    Yup, set ocular once and forget it.  Yardage marking are never accurate ( might be if you have 20/10vissin and buy top shelf) and changing the ocular also would/will change the range/focus. Just put tape over the marking, use a tope measure/laser r range finder and mark accordingly.

     I must not usnerstand, your scope is clear at 5x only?  Or, greatly needs to be re focused after power setting change?
    If you focus at max power, then drop down it should still be in focus.
     Make sure you have eye relief correct- head bobbing &  – and use it some more with bright light and maybe try clicking ” box’s” as your scope isn’t sounding all that good (???) so far but maybe still just needs adjustment, might as well see if click repeat while it’s new.

    John
     

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    pete72
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    to better understand.  if I were at 5 power on the scope and adjust the objective so it is clear then decide to increase to 9 power magnification and leave the objective lens where it was at 5 power the target is now not clear. so do I have to readjust the front objective to make things clear again? does changing magnification power  change my objective focus?

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    pete72
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    maybe I need to leave the objective set to infinity  as this is where I set my ocular focus? or maybe just set the scope power to 9 and redo the ocular focus then use the objective focus? am I making any sense??  

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    The ocular focus is just for the reticle. Once you focus so the reticle is nice and clear you don t ever have to touch it again. The adjustable objective (parallax adjustment) is what your going to use for all your focusing needs at different distances. The distance markings arent necessarily spot on.

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    30cal
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    Yes you do have to adjust your focus (parallax) as you are shooting. Just like with binoculars. The big end of the scope or side focus knob if it has that. The small end (closest to your eye) is set once and forget.

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    JohnL57
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    The higher the magnification, the more critical focus is. At low magnification the depth of field, (that is the area in front of and behind the focal point) is larger so focus is less critical.Hope that makes sense. This is why Field Target shooters use very high magnification scopes to range their targets.
    John

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    pete72
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    so just for fun lets say I’m shooting at a 20 yard distance  and my scope is at 4x  and I have it where its focused clear with the objective which is a little pass the scope 20yrd objective factory mark. now I want to change to 6x power or maybe a little more the scope gets a little fuzzy. do I just readjust the objective to clear it up and not pay any attention to the yardage marks on the ao? lets just say I need to have the objective set to 40 yards or wherever to make clear again at the increased magnification? is this proper?

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    30cal
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    Yes. Just focus as needed. You have to be able to see what your shooting at.

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    plano_harry
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    As John said, you are seeing the effect of depth of focus field. If you focus your objective at 9x and back off to 4x, it should still be sharp. Doesn’t work the other way around because the focus is too deep at 4x to get it right on visually, so you see the error when you get to 9x

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