Solar-Altitude Azimuth

A quantitative study of the systematic and accidental errors that affect solar-altitude azimuths shows that the precision of azimuths can be increased materially by taking into account the systematic errors due to curvature and semidiameter. When this is done, the elapsed time of an observation may be extended without affecting precision. The hour-angle criterion for determining when, during the day, observations should be taken has limitations that may be overcome by use of a more appropriate criterion, the rate of change of the sun's azimuth with respect to altitude. Pointings on the sun, using the quadrant-tangent and center-tangent methods, is very precise. In general, the closer an observer is to the equator, the higher the precision of a solar-altitude azimuth determination will be. At latitude 40○ N or S, the probable error of an azimuth determined with a 1-min transit, using no special equipment other than an eyepiece prism, is approximately ±15 sec.