Computation of times of sunrise, sunset, and twilight in or near mountainous terrain

Bill C. Ryan

Treesearch

Computation of times of sunrise, sunset, and twilight in or near mountainous terrain

Informally Refereed

Authors:

Bill C. Ryan

Year:

1977

Type:

Research Note

Station:

Pacific Southwest Research Station

Source:

Res. Note PSW-RN-322. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 4 p

Download (PDF 290 KB)

Download (PDF 290 KB): https://research.fs.usda.gov/download/treesearch/31327.pdf

Abstract

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

Citation

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