The American Ephemeris and Nautical Almanac Volume 980

The American Ephemeris and Nautical Almanac Volume 980

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 edition. Excerpt: ...About March 21st of each year the sidereal clock agrees with the mean time, or ordinary clock; and the former gains on the latter about 3m 56 per day, so that at the end of a year it will have gained an entire day, and will again agree with the mean time clock. Day.--The Civil Day, according to the customs of society, commences at midnight, and comprises twenty-four hours from one midnight to the next following. The hours are counted from 0 to 12 from midnight to noon, after which they are again reckoned from 0 to 12 from noon to midnight. Thus the day is divided into two periods of 12 hours each;, of which the first is marked A. M., and the last is marked P. M. The Astronomical Day commences at noon on the civil day of the same date. It also comprises twenty-four hours; but they are reckoned from 0 to 24, and from the noon of one day to that of the next following. The astronomical as well as the civil time may be either apparent or mean, according as it is reckoned from apparent noon or from mean noon. The civil day begins twelve hours before the astronomical day; therefore the first period of the civil day answers to the last part of the preceding astronomical day, and the last period of the civil day corresponds to the first part of the same astronomical day. Thus, January 9th, 2 o'clock, A. M., civil time, is January 8th, 14h, astronomical time; and January 9th, 2 o'clock, P. M., civil time, is also January 9th, 2h, astronomical time. The rule, then, for the transformation of civil time into astronomical time is this: --If the civil time is marked A. M., take one from the day and add twelve to the hours, and the result is the astronomical time wanted; if the civil time is marked P. M., take away the designation P. M., and more

Product details

  • Paperback | 40 pages
  • 189 x 246 x 2mm | 91g
  • United States
  • English
  • black & white illustrations
  • 1236966015
  • 9781236966018