Set the scope (or rifle/scope combo) aimed at the desired distance. Move your eye back and forth behind the scope. Do the crosshairs move across the target? If yes, parallax is present, and the scope is a candidate for this adjustment. Note: Having the reticle (crosshairs) way off center can also cause parallax, and this procedure may not correctly fix that problem. You may wish to recenter your reticle first.
Most cheap scopes have a Lock Ring at the Objective end that retains the objective. It is generally finished to appear matte or smooth, as appropriate, and to blend and not look too obvious. It is lock-tite'd in place. The most difficult part of the procedure is breaking the seal. You do this in the same manner as opening a difficult jar of ketchup. Unscrew the Lock Ring all the way off of the scope.
You'll see that the objective lens is held in place inside another ring, and that ring has two slots opposite each other. I'll call that the Objective Carrier ring. A thin, strong bar of steel (such as an old auto points file) can be used to adjust the objective in the same manner as an AO scope. Be careful not to scratch the lens.
Wait a second, you're thinking, I know how to adjust the Objective on an AO scope because it's marked in distance. How do I know how to do it on an unmarked scope?
That's the tricky part. You do it by trail and error. If the old page were up, or I had a photographic memory, I might remember whether in/out is long/short distance, but I don't.
Adjust the scope objective lens assembly inward (inward is preferable to start with, as it is less likely to cause the scope to lose its airtight seal). Check parallax (don't worry about focus too much right now). Did it increase or decrease? Move it in or out as necessary. When you seem to be getting close, take note of the objective carrier's slot position so that you can return to an old adjustment.
After the Objective is set, the eyepiece will have to be readjusted for focus. I saw a post here recently that mentioned that the AO (Adjustable Objective) is how to focus a scope for a certain distance. That is incorrect. That is what the eyepiece is for, but for all distances. Undo the eyepiece lock ring (much easier since it is made for user adjustment) and adjust it for simultaneous focus of the reticle (crosshairs) and the target. When it is correct, you should be able to look at the target over top of the scope, and then through the scope, without having to adjust your eye focus, and have everything look clear.
Replace the Objective locking ring, being careful not to rotate the Objective carrier ring. If you are supremely confidant, you can use one of the lesser lock-tites.
How much? A friend using this technique and forwarded these notes on the condition of anonymity (*#%@ spammers):
I successfully adjusted the parallax distance of (2) inexpensive scopes last evening, a Simmons Deerfield 3x-9x, 32mm that I purchased at Wal Mart recently for about $32, and a Bushnell Sharpshooter 3x-9x, 32mm that I purchased some 7 years ago for about $30. Here is what I found: 1) Using the instructions from your web site, this adjustment was pretty easy to perform - thank you. 2) To adjust from a farther distance to a shorter distance, you want to move the objective lens further OUT of the scope tube (i.e., move the objective lens towards the target). 3) The adjustment is pretty fine. I don't know what the factory parallax settings of these two scopes were, but on the Bushnell, I needed to move the objective lens out 1.1 mm, which required 1.625 turns. The Simmons required 0.81mm, provided through 1.125 turns. I adjusted the parallax at 13.5 yards (this being the maximum distance afforded by doing this inside my house, but checking at appropriate airgun distances outside proved the adjustment was good.).
If anyone else has anything more to add, I'll be glad to add it to my page, with or without citation, as you desire.
Hope this helps!
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