Abstract: An optical gun sight system for an M1A2 Abrams Main Battle Tank supported in a lower housing which may be attached to the fixed internal upper housing in the turret of the tank. An adapter plate is provided which has two sets of openings, one to align with the openings in the upper housing and the other to align with openings in the lower housing. An alignment mechanism allows for fine adjustment of the lower housing relative to the upper housing. Operating buttons, knobs and filter wheel are conveniently located on or beneath the front face of the lower housing. A thermal imaging system includes an objective lens for receiving an image of a target object, an eyepiece lens for viewing the image of the object, and a compensator lens movably located between the objective and eyepiece lenses for providing a thermal image of the object.