Before GPS, a primary navigation method for ships, aircraft, spacecraft and missiles was celestial tracking, also known as astronavigation. The basic approach is to sight on the sun or a particular star and calculate the position of the aircraft, missile or ship from the sighting angles to the star. The calculation is based upon highly accurate data about the positioning of the sun and certain reference stars at various time and locations. For modern applications, the star tracking location is used to calibrate and update an inertial navigation system.
Early Air Force aircraft such as early B-52 bombers relied on a human using a sextant through a bubble in the top of the plane. Some time in the late '60s, manual sighting was replaced on the E and F models by this automatic astro tracker mechanism and its associated analog computer. At some point, the astro navigator was replaced by GPS. Our device has a maintenance tag dated 1983, so the system was used at least until then.
Similar "star trackers" were and are used on many other planes such as the SR-71 and RC-135 reconnaissance aircraft, the B-58 bomber, and the P-3 Orion patrol plane. Of special interest is the fact that the most modern USAF plane, the B-2 bomber, still has a automatic star tracker navigation system. Many missiles, including some currently operational ones, also use automated start tracker navigation: the Polaris, Poseidon, Trident, MX, SM-62 Snark and the AGM-28 Hound Dog, and others.