Illumination is especially subject to by a battery powered LED, though other electric brilliant sources can be used. The phosphorescent is projected forward through the scope, and reflects off the behind surface of the reticle. Bloodshot is the most casual colour used, as it least impedes the shooter's dark vision.

Parallax problems result from the image from the objective not being coincident with the reticle. If the image is not coplanar with the reticle (that is the image of the objective is either in front of or behind the reticle), Rifle Scopes then putting your eye at different points behind the ocular causes the reticle crosshairs to appear to be at at variance points on the target. This optical end causes parallax induced aiming errors that can make a telescopic exhibit user miss a inconsiderable target at a distance where the telescopic display was not parallax adjusted for.