The American Ephemeris and Nautical AlmanacU.S. Government Printing Office, 1920 |
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Page 743 - Therefore clocks and chronometers can not be regulated to apparent solar time, which may, however, be determined by observations of the Sun when visible. Mean Solar Time is measured by the motion of a fictitious body called the mean Sun, which is supposed to move uniformly in the celestial equator, completing the circuit in one tropical year. Since mean solar tune is uniform and regular in its passage, clocks and watches may be regulated to it, and those in ordinary use are usually so regulated.
Page iii - Tork in preparing the different national nautical and astronomical almanacs and increasing the total data which may be of use to navigators and astronomers available for publication in the American Ephemeris and Nautical Almanac...
Page iii - The Secretary of the Navy is hereby authorized to arrange for the exchange of data with such foreign almanac offices as he may from time to time deem desirable with a view to reducing the amount of duplication of work in preparing the different national nautical and astronomical almanacs and increasing the total data which may be of use...
Page xviii - Conjunction, or having the same Longitude or Right Ascension. П Quadrature, or differing 90° in " " " ¿> Opposition, or differing 180° in " " " fi The ascending, у the descending node.
Page iii - That the work of the Nautical Almanac Office during the continuance of any such arrangement shall be conducted so that in case of emergency the entire portion of the work intended for the use of navigators may be computed by the force employed by that office, and without any foreign cooperation whatsoever: Provided further, That any employee of the Nautical Almanac Office who may be authorized in any annual appropriation bill and whose services in whole or in part can be spared from the duty of preparing...
Page 745 - The Sun's Semidiameter and the Sidereal Time of Semidiameter Passing Meridian are also given on page I. The Sun's semidiameter is used in reducing the altitude of the upper or lower limb of the Sun to the altitude of the center; and in reducing the angular distance between the limb of the Sun and the Moon or other object, to the distance from the center of the Sun.
Page iii - Provided further, That the work of the Nautical Almanac Office during the continuance of any such arrangement shall be conducted so that in case of emergency the entire portion of the work intended for the use of navigators may be computed by the force employed by that office, and without any foreign cooperation whatsoever...
Page 743 - The Equation of Time is the difference in hour-angle between the true Sun and the mean Sun. The true Sun is sometimes before and sometimes behind the mean Sun by an amount which varies from zero to about 16 minutes.
Page 615 - X is taken equal to the ratio of the illuminated portion of the apparent disk to the area of the entire disk regarded as circular.
Page 743 - Day (solar) — Time interval between two consecutive transits of the Sun over a meridian. Since this time interval varies with Earth's orbital motion, a mean solar day was chosen, based on a mean annual motion of Earth (assuming an equivalent circular orbit) or a fictitious mean Sun.