Telescopic sights commonly include a reticle which is laterally moved to adjust for the point of aim. In this invention, a prismatic device is used to move the image of the target on the reticle. In one embodiment, a pair of prisms are placed in the optical path of a telescopic sight such that at least one prism is movable along the optical axis. The point of aim is adjusted by adjusting the distance between the two prisms. By replacing the lateral movement of the reticle with the longitudinal movement of a prism, this invention eliminates several drawbacks associated with the prior art including limitations in the adjustment range.