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Crater shadowing effects at low sun angles, part QA comparison of Apollo 15 lunar surface photographs taken at low sun-elevation angles with photographs of an experimentally cratered surface at low lighting angles is discussed. The comparison revealed marked similarities, the most significant being that the smallest craters in both sets of photographs are filled with shadows that form beadlike chains and clusters. It was also found that the fraction of area covered by shadows within the smaller craters is so large that 30 to 40 percent of the total field of view is covered by shadow. It is concluded that: the fraction of area covered by resolvable craters, which should be somewhat less than the fraction of area covered by shadow for photographs with very low sun elevation angles, may be calculated using the steady state crater frequency distribution for craters from 20 to 100 m in diameter and then adding the area covered by larger craters for which the crater frequency distribution has the form of the crater-production frequency distribution.
Document ID
Document Type
Moore, H. J. (Bellcomm, Inc. Washington, DC, United States)
Date Acquired
August 6, 2013
Publication Date
January 1, 1972
Publication Information
Publication: NASA. Manned Spacecraft Center Apollo 15 Prelim. Sci. Rept.
Subject Category
Distribution Limits
Work of the US Gov. Public Use Permitted.

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