Gun Glossary
Parallax:
In telescopic sights, the condition that exists when the reticle (crosshairs) does not lie exactly on the image plane. Excessive parallax makes the shooter's eye position very critical if repeatable accuracy is to be obtained. Most lower power scope have the parallax pre-set at 150 yards; high-magnification scopes (10X and up) commonly have an adjustable objective to correct for various distances.
