Parallax adjustment

[Bob Kingsbury]

I recently added a new scope to my gun. Its 40X the same as the others I
have on BR rifles. I noticed today, that when the focus is very sharp, I still had
some parallax. Adjusting it slightly off peak sharpness , parallax was better. What
causes this?

2nd question, You have just arrived at an afternoon match, and the mirage is bad.
How could you adjust parallax out

 

[Wayne Shaw]

You need to tweak the back end along with the front end, and you'll get it out.

Light changes all day long. Adjusting to compensate is part of the game. If you cant adjust out parallax, the scope should be looked at. Regular eye exams help too.

 

[Boyd Allen]

IMO the eyepiece has quite a bit more depth of field (focus) than the objective, which can lead to a situation where the cross hairs look fine even though the eyepiece is not focused precisely in the plane of the reticle, which it must be to have both peak target image sharpness and no parallax. As Wayne wrote, what you need to do is to make small moves alternating between the eyepiece and parallax adjustments. I would first remove all the parallax, and then refocus the eyepiece to get your target back in peak focus, then check parallax and so on, until you have both zero parallax and your best target sharpness. The whole "focus the eyepiece once, like this, and lock it down forever" business completely ignores the very real possibility that one's first attempt may be just a little off, and the evidence is the situation that you have described.

 

[John Kielly]

Am I correct in assuming that there is a difference in the method (theory, perhaps) of removing parallax from a scope that uses the side adjustment compared with those that adjust on the objective?

It has been my experience that clearing parallax whilst retaining sharp focus is easy with the latter, while every side adjustment scope I have used is somewhere between difficult & impossible to adjust.