The American Ephemeris and Nautical AlmanacU.S. Government Printing Office, 1892 |
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Page 512 - ... used for greater precision. Page XII contains also the Phases of the Moon and the dates of the Moon's Perigee and Apogee, or least and greatest distances from the earth. Pages...
Page 507 - A Solar Day is the interval of time between two successive transits of the sun over the same meridian ; and the hour-angle of the sun is called Solar Time.
Page 508 - January 9th, 2'1, astronomical time. The rule, then, for the transformation of civil time into astronomical time is this: — If the civil time is marked AM, take one...
Page 510 - The sidereal time of semidiameter passing the meridian is employed in obtaining the passage of the sun's center over the wires of a transit-instrument, when the passage of one limb only has been observed. The quantity found in this column is to be added to the time of transit of the first, or western, limb; and to be subtracted from the time of transit of the second, or eastern, limb. Page II contains, for Greenwich mean noon of each day, The Sun's Apparent Right Ascension and Declination, the Equation...
Page 515 - ... In Longitude is the correction to be applied to the longitude of the body referred to the mean equinox, in order to obtain that longitude as referred to the true equinox. When the correction is positive, the true longitudes are greater than those referred to the mean equinox; while the contrary is true when the correction has the negative sign. The equation In RA is equal to that in longitude, multiplied by the cosine of the obliquity of the ecliptic. The next column gives the Precession of Equinoxes...
Page 513 - Navigator (Table 45}, subtract the PL of Diff. taken from the Almanac. The result is the proportional logarithm of an interval of time to be added to the hours of Greenwich time, taken from the Almanac, when the earlier Almanac-distance is used; to be subtracted from the hours of Greenwich time, when the later Almanac-distance is used.
Page 508 - January 4th, 11 o'clock, AM, civil time. If the longitude from Greenwich be expressed in time, and, when west, added to the local time, or, when east, subtracted from the local time, the result is the corresponding Greenwich time. If the local mean time is used, the result is the Greenwich mean time, which ordinarily is that required for the use of this Ephemeris. The rule is the same, whether we use mean or sidereal time. THE CALENDAR. The Calendar is divided into twelve months, and to each month...
Page 507 - ... of the sun is called Solar Time. This is the most natural and direct measure of time. But the intervals between the successive returns of the sun to the same meridian are not exactly equal, owing to the varying motion of the earth around the sun, and to the obliquity of the ecliptic.