How does reticle point at the target ?

In a purely mechanical and optical scope(no electronics, no software), how does reticle or crosshair point directly at the target?

What is the mechanism that enables reticle to aim at the target?
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David Johnson, CD, MVPRetiredCommented:
the recticle will move up or down or left to right depending upon the distance (using click stops) by experience you know at a specific range to target you have to adjust the elevation up or down x # of clicks from the calibrated setting.  Then again by constant testing you can adjust the windage for the wind velocity and direction.. one click could be one inch change at 200 yards and 1 foot at 1000 yards.  One may not even change the scope settings but instead use the mill markers inside of the scope (one mill up, two mills right and use that as that as the aiming point  instead of the center of the recticle.  

There is a huge difference between good enough and getting the gold medal
Dr. KlahnPrincipal Software EngineerCommented:
The reticle doesn't "point" anywhere.  It is only half of the system, and the fixed part at that.  Where a round hits depends on where the rifleman's eye is located behind the exit lens.

When the rifleman's eye is correctly and repeatably located on the optical axis this is the desired condition for accurate and repeatable shooting.  When that is the case, placing the reticle over the target causes the round to land on-target when (a) the optical system is calibrated correctly and (b) the rifle is located at the same distance from the target for each shot..

If the rifleman's eye is located off the optical axis, even if the optical system is calibrated correctly and the rifle is located the same distance from the target for each shot, placing the reticle over the target will cause the round to land off-target.  Only when the rifleman's eye is on the optical axis can a reticle be considered to be an accurate aiming aid.

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naseeamAuthor Commented:
>> "calibrated setting"
What is calibrated setting?  Is it when scope is turned ON will objective lens covered?  If yes, what is calibrated?

>> "The reticle doesn't "point" anywhere.  It is only half of the system"
I don't understand this statement.  Please explain.

>> "exit lens"
Is that ocular lens or objective lens ?

>> "optical axis"
What is optical axis?
David Johnson, CD, MVPRetiredCommented:
Scope is short for telescope, the difference is that there is in approximately the middle an aiming point it could be a dot, a post, a cross-hair, a mix of a post and a cross-hair,  When you initially sight in the scope (calibrate it)  +/- 0 elevation +/- 0 windage at a measured distance. All bullets travel in an arc, usually the higher the velocity the shallower the arc.  all bullets as they travel through air slow down and the bullet curves downward.  One would adjust the scope so that the bullet hits the target exactly where the cross hairs were when the rifle is fired.  Depending upon the weight of the bullet, the muzzle velocity where the rifle is aimed to hit a target will be different than if you looked down the barrel (this is called bore sighting) the bullet will be higher or lower (due to trajectory) than where the barrel is aimed at.

the optical axis is the center of the eye-piece in a straight line to the center of the objective lens.

What is calibrated setting?  Is it when scope is turned ON will objective lens covered?   I'm guessing you meant to say 'when the objective lens is covered)
Most scopes are not electrical in operation they are optical devices (there is no on/off)
Perhaps this video may help
naseeamAuthor Commented:
Nice explanations.  

Expert provided key information about reticle.
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