Originally Posted By: stuart_hayes Originally Posted By: who meI remember something about standing the scope on a mirror objective down. While looking through eyepiece you would see two sets of crosshairs in the reflection of the mirror. You would then adjust the windage and elevation until you saw only one set of crosshairs. I never tried this, maybe someone else will also remember reading about doing that.
+1 tried mounting it and dialing it and ran out of adjustment, used the mirror got me back to "center" or what is called mechanical zero.
Above is one way of doing it...and it can be called "mechanical zero" but it is more accurate to call it "optical zero." Mechanical zero is talked about further back in this string when the gentlemen suggested turning the turrets while counting and then split the difference. All things being perfect both the "mechanical" and the "optical" zero should be one in the same. But, they rarely are. Another way to find optical zero is to place the scope in two vee blocks and spin it while adjusting the turrets so that eventually when spun the reticle center remains centered on a fixed spot as opposed to rotating in orbit around the fixed spot. The significance of being optically zeroed is that you can then do as much as possible zeroing bullet impact with shims for elevation and {one way} Redfield style bases, i. e., to ideally have bullet impact and as close to perfect optical zero as possible. This insures as much light as possible is centered between the eyepiece and objective lenses for the best view/light gathering the scope can possibly have. Maybe a better way to explain it is that the scope is adjusted not by moving the actual crosshairs but by moving a "washer" around in the tube with a smaller opening. If you think of the light entering the scope as water sprayed out of a hose imagine the difference between that water sprayed straight thru a pipe or sprayed thru a pipe with an offset washer in the middle. More light for a better view gets thru a scope that is optically centered.
