LONG-WAVE RADIO TRANSMISSION PHENOMENA 19 



APPENDIX II 



Determination of Sun's Altitude and Azimuth 



The angle of the sun to the horizon and to the meridian plane at any 

 hour may be computed by methods similar to the above. F'or this 

 case we have a celestial triangle whose sides are a meridian through 

 the observer's zenith, a meridian through the sun, and a great circle 

 through the sun and the zenith. The arc subtended by the pole and 

 zenith is the complement of the observer's latitude 'V." the arc sub- 

 tended by the pole and the sun is the complement of the sun's declina- 

 tion "d" (celestial latitude), and the angle "/" at the pole between 

 these two arcs is the sun's hour angle. With these two sides and 

 included angle we may compute the arc between the sun and the zenith 

 (complement of the altitude " h") and the sun's azimuth "s" which 

 is the angle between the meridian containing the zenith and the great 

 circle passing through the zenith and the sun. 



By the law of cosines (1) above 



(8) sin h = sin d sin <p + cos d cos (p cos / 



and by the law of sines 



,r,\ • r, sin t cos d 



(9) sm Z = -. — • 



cos h 



Values of h and z as a function of (p, d and / are tabulated in con- 

 venient form in hydrographic office publication H.O. No. 203. The 

 sun's declination and the computed times of sunset may be obtained 

 from the American Nautical Almanac. 



