1. A method for boresighting of a designation system, including a tracker responsive to a detector with reference to an indicator, comprising the steps of: (a) directing a beam of light at a target, using a light source, so that said beam of light is reflected from a spot on said target while a temperature of said spot remains substantially constant; (b) focusing at least part of said reflected light as an image on the detector; and (c) determining a misalignment of the indicator and said image.