Abstract: A line-of-sight corrector using piezo-electric crystals as actuators is provided for the inertial platform stabilized tracking telescope of an astro navigational system. The tracking telescope in the embodiment of the invention to be described herein includes a folded-type optical system, and the corrector is used to impart movement to the secondary mirror in the folded optical system to compensate for residual angular movements of the telescope which would otherwise perturb the image focused on the vidicon or solid state sensor in the telescope.