Recognition of Lunar Craters

Abstract

Recognition thresholds for lunar crater size were determined, analytically, for various look angles and magnifications, at an orbital altitude of 80 nautical miles. Elliptical image measurements for various sized craters were combined with some previous threshold recognition data for the ellipse (Casperson, 1950). Elliptical image measurements consisted of the visual angle of the major axis, and elliptical form (the ratio of minor axis to major axis). A computer program was generated from which the visual angle and form measurements of anticipated elliptical crater images were computed for various combinations of crater size, look angle, and magnification. Casperson's data was then re-worked to obtain the visual angle and form measurements associated with his recognition threshold data for the ellipse. By graphically combining the visual angle and form data from both computations, 50% and 75% threshold recognition curves were generated, relating crater size, magnification and look angle. Implications of these data are discussed.