A reticle for a guidance seeker for spinning projectiles comprises a substrate; a pattern of a plurality of alternating light modulating structures, such as opaque and light transmitting, or light absorbing and light reflecting areas on the substrate such that an image of a target moving on the substrate will generate a plurality of pulses corresponding to the number of lines crossed by the image, the number of pulses increasing as the image moves outwardly from the center of the reticle; and a distinguishable, unambiguous, and singly periodic feature of the pattern, which is readily detectable every time the target image moves circumferentially, completing a full circle around the center of the reticle.