AO adjustment

[waterman]

Still new to all this stuff. My question is I have sighted my rws 48 .177 at 10 yds and have calculater my poi for 30,40 and 45 yds Now if I change my ao adjustment to say 30 yds will calulation stand or will my scope move for a new shot. thanks  Waterman
PS I am havin a blast

[yoda4561]

Unless the scope is defective the A.O. or side focus adjustments will not change your POI.

[waterman]

Thanks Yoda I was hoping that was the case.

[GunnerAl]

waterman, all you have to worry about with that AO is the parallax issue, and DON'T take the distances on the adjuster as gospel. They're more often than not totally inaccurate. Make those adjustments manually. Just ask if you don't understand or wish us to elaborate in the parallax thing. You wont be the first one to misunderstand it because it can be misleading...

[waterman]

I have my AO set at ten yds for inside and so I can see. Now I go rabbit hunting and set AO to 25-35 yds My sloppy math tells me I'm -.6 at 10yd and +.13 at 30yds Will that stay the same?   thanks

[GunnerAl]

Where you set the point of impact should NOT change as you adjust for parallax. They are two different parts and adjustments of the scope and should not interfere with each other. It IS possible however, that they may just alter a bit when adjusting either one or the other, but that's not usual.

So when you sight in, for example zeroed at 20yds,, and you fire at a target at 20yds, you need to set the AO or parallax adjustment properly for 20yds (or 60ft on some scopes). If you then start firing at targets at say, 40 yds, you then need to readjust the AO or parallax adjustment for 40 yds (or 120ft)... The point of impact will NOT be altered,, that's still zeroed at 20yds so you need to hold for drop or rise, whichever. We are now talking AO or parallax adjustment here NOT point of impact which stays put once you have sighted in,, OK...!!!

[GunnerAl]

I'll try further to explain parallax...

Parallax correction is so the image coming from the scope into your eye appears to be one image only, when infact you are geting two - The first image is of the target or whatever you are pointing the scope at. The second image is the reticle (crosshair) which is always at the same fixed distance inisde the scope. If you point the scope at a target at say 20yds, the lenses may be at slightly different focal lengths for the crosshair to stay fixed in the centre of the image, so moving your eye across or up and down the image may look like the crosshair is moving across the target, almost with your eye. This means there is a slight amount of parallax between the two images. Adjusting the AO will change the focal length of the imcoming image (the target) and align it with the existing image of the reticle (crosshair) and when adjusted properly no matter where you move your eye, the crosshair will always appear to stay in one fixed place on the target... Of course, as you aim at further or closer targets, you need to alter that AO adjustment to compensate for the new distances involved again... That's what is needed to get the best shooting accuracy results.

The zeroed distance (POI or Point Of Impact) will always stay at the same distance until you re-zero it...

[GunnerAl]

Just a bit more,,

If you were into photography, you would completely understand this concept of parallax. Sometimes it is a very desired effect and one that we may adjust to "get" rather than to "get rid" of, when taking a photo. It's better known as Depth of Field or something similar to it, so that when it exists it tends to make the photo look, well, almost as if there was a third dimension of depth or distance in it, so closer objects appear to actually be closer instead of everything all on the same plane, like we need from a telescopic sight... Of course in a camera, there is a lot more to it than just parallax adjustment, as you have lots of adjustments at your fingertips but it is very similar to that in your telescopic sight...

[palonej]

Great explanation on a confusing subject Al.
I'm pretty sure I recall someone posting about a lower end Hawke scope that was moving POI laterally when shooting at different distances. Can't remember the model, but the only time this happens is with a defective scope. POI should not change.

[GunnerAl]

The only scope I ruined, in modern times anyway, was a Hawke HD Sports, well used on quite a few air rifles. One day I noticed things just looked a bit blurry through it. I think it was only on a BSA Meteor Mk4 at the time, nothing to get all upset about with its whole 650fps rating .177 but it was on a Cometa Fenix 400 before that,, anyway I put the rifle down and wiped my eye, back up, ahh fine, fired a shot, loaded again, went to fire, blurry. After a few minutes and a handful of more shots, all over the target, I found the objective lens was loose and moved back and forth about 3 or 4 mm (1/8th" approx or more) in its seating. Ahhh, now I knew. I got it replaced under its lifetime warranty. Touch wood, I hope that was the first and last time...

That episode sure shifted the POI while I was sorting it out...