Optical measuring apparatus

Claim 1

APPARATUS FOR DETERMINING THE ORIENTATION OF A REFERENCE MIRROR WITH REFERENCE TO TRUE NORTH COMPRISING: (A) A NORTH REFERENCE MIRROR ORIENTED APPROXIMATELY PERPENDICULAR TO TRUE NORHT; (B) RECORDING MEANS HAVING A FLAT SURFACE FOR PROVIDING A PERMANENT RECORD OF ANY LIGHT IMPINGING UPON SAID FLAT SURFACE, SAID RECORDING MEANS HAVING SEMIREFLECTING CHARACTERISTICS; (C) OPTICAL MEANS FOR OPTICALLY CONNECTING SAID NORTH REFERENCE MIRROR TO SAID FLAT SURFACE OF SAID RECORDING MEANS AND FOR RECEIVING STARLIGHT AND FOCUSING SAID STARLIGHT ONTO SAID FLAT SURFACE, SAID STARLIGHT FOLLOWING ARCUATE PATHS ON SAID FLAT SURFACE OVER A DEFINITE PERIOD OF TIME; (D) LIGHT PRODUCING MEANS; AND (E) MEANS FOR TRANSMITTING A BEAM OF LIGHT FROM SAID LIGHT PRODUCING MEANS ONTO SAID FLAT SURFACE OF SAID RECORDING MEANS IN A MANNER TO PRODUCE A FIRST IMAGE ON SAID FLAT SURFACE, SAID RECORDING MEANS PARTIALLY REFLECTING SAID FIRST IMAGE THROUGH SAID OPTICAL MEANS ONTO SAID NORTH REFERENCE MIRROR AND SAID NORTH REFERENCE MIRROR REFLECTING SAID FIRST IMAGE BACK THROUGH SAID OPTICAL MEANS ONTO SAID FLAT SURFACE TO PRODUCE A SECOND IMAGE ON SAID FLAT SURFACE DISPLACED FROM SAID FIRST IMAGE, THE PERPENDICULAR TO SAID NORTH REFERENCE MIRROR BEING INDICATED BY A POINT ON SAID FLAT SURFACE EQUIDISTANT BETWEEN SAID FIRST AND SECOND IMAGES ON A STRAIGHT LINE CONNECTING SAID IMAGES AND TRUE NORTH BEING INDICATED BY THE CENTER OF THE ARCUATE PATHS PRODUCED BY THE INCIDENT STARLIGHT ON SAID FLAT SURFACE.