Parallax

I posted this over on the yellow in response to an often ask question on parallax adjustment.

Somehow, parallax is still to this day, mis-understood by many shooters. With even less understanding of how to adjust for it. Soooo, I desided to post this little How-Too.

Mike

——————————————————————————–

Beeing an optic nut, I am dismayed at just how many times the basics are missed. And is being missed once again here. By folks that shoot often and should know better.

Perhaps it is the terms that have crept in to confuse us all.

There is the AO, which is usually used to describe the front parallax adjustment on the bell of the scope. This is the “Objective” lens adjustment, and sets the parallax at a given distance. (This being the focal plane being shifted from in front of the cross hair, on the cross hair, or behind the cross hair. When the focal plane falls either fore, or aft of the cross hair, we get parallax. (And a HUGE Reason First focal plane scopes are so well thought of in Military Sniper Scopes. They are virtually parallax free) But most of us use 2nd focal plane scopes. So we have to deal with it!

In a 2nd focal plane scope, the type most of us use, The cross hair remains the same size. It increasses in a 1st focal plane scope with magnification. (Somthing most of us don’t for Air Guns. Since we have such small targets, and vital areas on game). So for this post, I will focus (Pun intended) on our 2nd focal plane scopes.

On the modern side focus scopes, for SF scopes, the term has been used so much that we take it for granted.
“BUT”, It is not a focus adjustment. (Although it is used many times to focus to get the range). It is a side Parallax adjustment. Why it is called something different when it is on the side I have NO Idea. Either will change the focus of the scope.

The Scope Focus in on the Eye end of the Scope. The “Ocular end”. And it must be set for the individual shooters eyes first. Before anything else is done. Period!
If you do not do this first, you have already handicapped your optical system. Any superior results, will be by pure blind luck.

Try this. First, Set the target at 50 yards, Set the side focus, (Yes, the side parallax adjustment for 50 yards. Pr the front p-adjustment for 50 yd’s. Which ever type of scope you have).

Do this before anything else. Look thru the scope. Is it clear? No? Time to go to work! Adjust the REAR adjustment (The one on the Ocular lens until the picture is clear. Not the cross hair, but the picture of the area being targeted. Stop there!

No set the scope to infinity. Look thru the scope. The sky is a good thing to use. It is after all, pretty much infinity. And the Cross hair really stands out there. Set the parallax adjustment until you have a clear crisp cross hair. Were not looking for a good picture here. Just a crisp cross hair. There yet? Yes? go to next step. No? do it again. Remember to take your eye away from the scope often. Your eye will try to do the adjustments for you. Which is fine, until you try to use the scope again, and it will be a blur!

Run the scope P-adjustment Back down to 50 yd’s again. How does it look on your 50 yard target? Close. Should be.
Different scopes will have slightly different focal points. So you will have to slightly adjust the AO to be completely crisp. Note where it is set at when completely sharp, focused on both the picture, cross hair, and Non-Movement of the Cross hair.

The fact that different scopes have slightly different focal plains. This is why some pay good money to have tuners make and Marked and aftermarket Side Adjustment wheels for their Scope-Gun Combo. Your scope height, fpe, pellet weight all figure into the markings as well, but that is not what we are looking at here.

Once you have followed this, try it at other yardages. And make fine adjustments when needed. Get lost, go back to infinity, and the sky, and start again. It has to be done from time to time.

Don’t forget to move your head, up-down-and side to side without touching the gun to see if the cross hair moves. It should not on a high quality scope with a good adjustabble parallax. Cheaper scopes can be very iffy. One of the reasons bench rest shooters pay the big bucks for Quality Optics.

Hope this helps.

Mike