Abstract: A device for automatically compensating for dynamic boresight errors between a visual line of sight and the apparent center of a beam of radiation emitted by the device. The radiation emitted by the device is used to guide a "beam-riding" missile to its target. Different sectors of the beam radiated by the device are modulated by different codes so that the missile can sense the apparent center of the beam. Optics within the device sense the extent to which the visual line of sight deviates from the apparent center of the radiated beam by means of measurements upon the coincidence of the visual line of sight and the apparent center of the beam of radiation within the device. The device then alters the coding of the radiated beam so that the apparent center of the radiated beam maintains alignment with the visual line of sight.