CAMERA PLATE‐REDUCTION BY MEANS OF STAR‐FIELD REFERENCE

The theory is developed for determining the direction of a point-object by photographing it on the same plate as a star field and using the stars as reference points. A minimum of three reference stars is necessary for determining the camera orientation and with more than three stars a least-squares solution is possible. The method of analysis involves the solution of simultaneous equations for nine “plate constants”. Once the plate constants have been found, the direction of an object may readily be obtained from the coordinates of its image on the plate. The six elements of orientation of the camera may also readily be found from the plate constants. Part of the theory has been programmed for the Pegasus electronic computer. An appendix gives a convenient method of applying atmospheric refraction corrections to direction cosines.