best thread ever on that subject.... http://www.gatewaytoairguns.org/GTA/index.php?topic=72099.0Bob
Thanks for the cheat sheet. One question: the little black "x"s are the center of the scope or a target spot?
The first revelation is that you don't WANT to rotate the scope 360*, in fact you want to rotate it exactly 180* during this operation......The reason for doing it this way is to be able to separate the two adjustments in your brain.
[The goal of centering is to] have the intersection of the crosshairs remain in the same place throughout the rotation. The way you do that is focus on one turret at a time. Doesn't matter which one you start with so I'll pick the windage. Orient the scope normally and take note where on the X-axis of your target the crosshairs rest. Then rotate the scope 180° and take note again where the crosshairs end up on the X-axis relative to the previous spot. Now adjust the windage turret to an imagined midway point between those two spots.Repeat this back and forth until the spot on the X-axis ends up in the same place when you rotate the scope 180°. While you are rotating the scope back and forth, you will probably notice the crosshairs orbiting against your target. You want to ignore that. All you care about right now is the X-axis and where the crosshairs end up left-to-right when the scope is oriented normally versus when it's upside down (rotated 180°). What it does in between those two points is of no interest.Once you have the windage fine tuned, now turn your attention to the elevation turret. Same idea except you're now focusing on the Y-axis.When you're done, you should be able to rotate the scope 360° and the crosshairs will remain in the same spot on the paper.
I'm sure that most of you (including me) that have tried using V-blocks to optically center a scope have found it a frustrating experience, fiddling with the turrents and seemingly making things worse instead of better.... Here is a simple diagram I made up to explain what is happening and hopefully a method to help you both understand what is happening, and use that knowledge to make the job a lot easier....The first revelation is that you don't WANT to rotate the scope 360*, in fact you want to rotate it exactly 180* during this operation, 90* to the left and 90* to the right (diagram is your view through the scope).... The reason for doing it this way is to be able to separate the two adjustments in your brain.... Most commonly you will see something like the right hand drawing.... In this example, when you rotate the scope CW 90*, the reticle ends up at about 4-o'clock (ie both low and right) and at 90* CCW it ends up at about 10 o'clock (high and left).... This error can be separated into the windage and elevation error, as shown in the other two diagrams.... If the windage is centered and there is only an elevation error, you will have the situation in the left drawing.... The end points are at 9 o'clock and 3 o'clock, in other words they are separated left and right, but at the same height.... If the elevation is centered and there is a windage error (middle drawing), the end points are at 12 o'clock and 6 o'clock, they line up horizontally, but at different heights.... How can you use this starting from the right hand drawing?.... You have already determined that both the height and width of the end points are moving.... Viewing a piece of graph paper as your target will help you with rotating the scope exactly 90* either way....1. Adjust the elevation so that the arc gets smaller, until the end points, when the scope is rotated 90* CW and CCW, are directly above one another (like the middle drawing)....2. Then adjust the windage so that the arc gets smaller and eventually disappears....Repeat steps 1 and 2 if necessary.... When you get the reticle centered in the tube, the aiming point of the reticle won't describe a circle, it will stay still and the crosshairs will just rotate around it like a propeller.... Your reticle is then centered in the tube....Bob
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