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SERIAL NO. 2631   PAGE 3.

tables and charts. While this method involves precomputation of the tables, it is felt that it is much better for a properly qualified person to spend considerable time in computations on the ground if by so doing an aviator without special training is required to perform the minimum number of operations in the air.

PRELIMINARY NOTES ON ASTRONOMY

The earth rotates on its own axis and at the same time travels in an orbit around the sun.

Due to the earth’s rotating from west to east, to a person on the earth the sun rises in the east, travels westward in a curved path across the sky and sets in the west.

On only two days in the year, March 21 and September 21, does the sun rise due east and set due west of the observer. In winter, the sun rises at some point south of east, rising as it travels southward until noon when it is at the highest point in its path for that day. T noon the sun is due south of the observer. Continuing westward the sun descends until it sets at some point south of west. In summer the sun rises at some point north of east and later is due east as it travels southward. At noon, it is due south but much higher in the sky than in winter. After noon it descends as it travels westward and some time before setting is due west of the observer. It sets north of west.

The path across the sky is different for every day of the year.

Noon is when the sun is due south of the observer. The sun is then said to be crossing the meridian, the meridian being a north and south line in the sky through the point directly over the observer’s head.

Noon is not at 12 o’clock standard time.

Due to the sun’s traveling westward, eight minutes after the sun is due south of Dayton it is due south of Indianapolis. The sun is due south of Belleville, Illinois, twenty three minutes after it has been due south of Dayton. In other