AO is off...should I be concerned

Longshot4

My 1978s old Redfield 12x with the OA is in tune thanks to this Forum. It's been at least 15 years since I have looked at scopes of that type. Correct me if I'm wrong but aren't the side focus scopes a new technology. Guys like my self still some times call the AOs focus. Do to the lack of keeping up with speed of it all.
 
Side focus scopes use an extra lens group between the objective lens and the erector/zoom lens group. Instead of its objective lens moving back and forth to focus the target image like AO scopes do, that extra lens group refocuses the target image from the objective lens through the erector/zoom group so it'll focus on the reticule.

It's all about bending light rays. Optical design software makes all sorts of imaging focus stuff much easier these days. It'll also help design the adjustment mechanics to move one end of the inner tube a given angular amount for click values desired. Some scope's adjustment click will move that tube 0001" or less.
 
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By Jove!!!!

I think I've got it! Bart B's comment about a "full turn off" got me thinking as well as the "all the way in" bit.

I ran the AO all the way in. I then measured off 50 feet (the lowest setting on the bell) and started cranking out 'till an object at 50 feet came into focus. It awhile , took maybe a full revolution out or more,....I wasn't counting.

Lo and Behold! The scale was very near 50 feet. I then set the scale on 100 yds and scoped my 100 rd target across the field. Clear as a bell,,,,I think. Did same drill with scope on another power setting and same results. There seems enough adjustment left to crank "in" the remaining settings at 200, 500 and 1000 and I'm betting those distances will be close on the scale as well.

I will double check tomorrow in better light....but I believe its good. My take is that the AO bell was cranked in/ out WAY to far one way or the other......(obviously its a used scope, and I've never had it on a rifle before) and was giving me goofy readings on the scale as a result. Zeroing the thing all the way in and coming out to a known close distance seems to have provided a solution.

Thanks all.
 
There is usually a "stop" inside to prevent over rotation, maybe it was dinged & no longer stops the bell rotating too far?
 
You can use a pair of binoculars to look through your rifle scope from different angles (up close and personal) to see greater apparent movement of the reticule to the target.

Anyway, after getting your scope well focused on a target at, say 50 yards, and it's parallax-free, mask the scope's reference mark with something then put a new mark directly opposite the "50" on the scope's AO barrel. It should be well focused and parallax free at any further ranges when that range number is at that new mark.

Found this web site page that might help folks understand parallax and focusing:

http://www.6mmbr.com/parallax.html

Note that the diagram's showing light from the target bends the same angle going through the outside edges of the objective lens regardless of the range to the target. If the target's close, the lens has to be moved forward, closer to it, to get those light rays focused on the reticule. If the target's further away, then the lens has to be moved back. The target image focus point moves back in the scope as the objective lens gets moved towards the target as it gets closer to the scope. The reverse happens if the target is further away. The target and its image move in the same direction and opposite of the direction the AO, be it either a barrel that turns on the front of the scope or a knob on the side of the adjustment turret.
 
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wrong

Well, I was wrong. The focus at 100 yds and out varies with the power setting. What is in focus at 100 at 6x, is not in focus at 9x and requires a change in the bell. When it does clear up, at 9x/100 +, the scale is not anywhere near the correct yardage. Pretty much back where I started. I have not experimented with groups and POI at various power settings, all my zeroing and groups were at 9x, which worked fine. I'm suspect now that the rifle will shoot to different points depending on the power setting.

I think the old scope may go back in the cabinet.
 
If the scope's eyepiece is not set right to make the reticule appear sharp and clear, it's possible that a target may appear a bit fuzzy if the AO is set at the target's range.

I suggest you set the scope's AO to a close range value, then look at a target that's exactly that range away. Then adjust the scope's eyepiece until both the target and reticule appear sharp. If this can't be done, then I suspect the scope's got some mechanical issues.
 
Ideally yo should set the AO at the highest setting & it should then be good for all lower settings at the same distance.
If you set it at lower power you might just be seeing the increase in magnification making it go "soft".
Its beginning to sound like there is something other than the scale being off happening here.
Try this & see what happens.

Rest the rifle so it can stay in place without holding.
Set the highest power for magnification.
Put a plain sheet of white paper in front of the front lens to reflect light into the scope. (usually a 45 degree angle works best.)
Briefly look into the scope & see if the reticule is immediately sharp.
If it isn't adjust the eyepiece focus until it looks sharp & then look away for a few seconds.
Go back to a quick look.
Repeat the quick look~adjust~look away~look back until it snaps into clear sharp focus when you first look in the eyepiece.
Remove the paper reflector.
Set a target up at a known distance. Visually focus the front eyepiece in the same look in~look away technique as you used before for the eyepiece.
Now slightly bob your eye up & down (or left right, either works) till the reticule doesn't "track" (move) in relation to the target.
Reduce the power setting.
do the eye bob again.

If the parallax changes as the power is reduced then there is something wrong in addition to the AO scale.:(
 
I've never been concerned about how accurate AO markings may or may not be. I just turn the adjustment until I see the best image. And it matters not to me if the reading on the dial is close to the target distance.
 
quits

I put the 6x Leupold back on the rifle. The old AO Weaver seemed OK, but there were so many peculiarities in the set up that I bailed on the whole idea.

Dang scope was likely to big on the rifle (size/weight) anyhow. The click adjustments were great, very responsive and the bullet holes moved around on target very gratifyingly, but the in focus/out of focus, what if...... just got to me.
 
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