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A Method for Calculating Moonlight Illuminance at the Earth's Surface
R. H. Austin, B. F. Phillips and D. J. Webb
Journal of Applied Ecology
Vol. 13, No. 3 (Dec., 1976), pp. 741-748
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2402251
Page Count: 8
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(1) A method of calculating the illuminance of moonlight reaching any location on the earth's surface, on any night of any year, is described. (2) Factors examined are whether the amount of sunlight is negligible, whether the moon is above the horizon, the changing distance of the moon, elongation or phase effect, atmospheric extinction, the angle of incidence of moonlight, and cloud cover. (3) A computer is used to calculate the variation in the illuminance due to each of the above factors, except the variation due to cloud cover, which is handled manually. The calculated variations are then used in the program to modify an arbitrary value of 100, chosen to represent the moonlight illuminance derived from the full moon, at the zenith, at a distance corresponding to the mean equatorial parallax. This is equal to 0.215 lux and relative moonlight illuminances can be converted to light values using this relationship. (4) Results of the use of the method are compared with the published results where measurements were made with a visual photometer. The comparison showed that the method is sufficiently accurate to be of value in ecological studies of marine and terrestrial nocturnal animals.
Journal of Applied Ecology © 1976 British Ecological Society