From these two diagrams, one can determine the approximate position of the sun with respect to the horizon of any place in the United States at any hour of the year. The sun's position with reference to the horizon is expressed by altitude and azimuth. Altitude is the angular distance above the horizon measured perpendicularly to the horizon. That line represents the celestial meridian, which the sun crosses at noon. Azimuth is the angular distance measured along the horizon in a clockwise direction.
Astronomers measure it from the south point, navigators from the north point.
The sun's daily path across the sky on or about the 21st day of each month is indicated by means of seven curved lines. The upper one is for June and the lower one is for December. Each of the other five is for two months. For instance, the path on March 21 is the same as on September 23. Each path is divided into hours.