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Pacific Southwest Research Station
800 Buchanan Street
Albany, CA 94710-0011
Publications and Products
Title: Computation of times of sunrise, sunset, and twilight in or near mountainous terrain
Author: Ryan, Bill C.
Source: Res. Note PSW-RN-322. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 4 p
Station ID: RN-PSW-322
Description: An electronic calculator with trigonometric functions can be used to compute times of sunrise, sunset, or twilight, or time of desired illumination at any location in mountainous terrain. The method is more convenient and versatile, and less cumbersome than using tables. Latitude, longitude, elevation, day of the year (1 to 366), and slope to the horizon at the azimuth of the sun at sunrise and sunset are necessary for the computations. The effects of elevation of the observation point and blocking of the sun's radiation by terrain surrounding the observation point are included in the computations.
Keywords: Length of day; mountains; sunrise; sunset; twilight; relief; slope; computation
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Ryan, Bill C. 1977. Computation of times of sunrise, sunset, and twilight in or near mountainous terrain. Res. Note PSW-RN-322. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 4 p.
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