The Nautical Almanac and Astronomical Ephemeris for the Year 1849

The Nautical Almanac and Astronomical Ephemeris for the Year 1849

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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. 1845 edition. Excerpt: ...Apparent and Mean Noon. Where time is deduced from observations of the Sun, the immediate result is apparent time; to convert it into mean time, the equation of time is necessary, and it is to be applied to apparent time, according to the precept at the head of the column. Thus, suppose the apparent time deduced from an observation of the Sun on January 16, 1849, in longitude 45 or 3h east of Greenwich, to be 6h, and it were required to convert it into mean time: Subtracting the difference of longitude 31' from the apparent time at the place, we have 3h for the corresponding apparent time at 3, gives 2'493 for the variation in 3 hours, and this being added (because the equation is increasing) to 10TM HSS, the equation of time at apparent noon, the result is 10m 11, -07, to be added (according to the precept at the head of the column) to the given apparent time 6h, whence we obtain 6" 10 1 1"-07, for the mean time required. At page I. of the month of April, we observe, at the head of the column tn/jt '/rm wl"ch signifies that a change of precept occurs in the course of the month; and between the equations opposite to the 14th and 15th days of the month, a black line, indicating that the change occurs between the Apparent Noons of those days. The upper precept applies to all the quantities above the black line; and the lower precept to all the quantities below it: that is, in the instance referred to, the Equation of Time is to be added to Apparent Time from the 1st of April to the instant at which the equation becomes 0TM 0, which happens between the noons of the 14th and 15th days of the month: but after that instant the equation is to be subtracted from Apparent to obtain Mean Time. Page II. of each Month. The Sun' more

Product details

  • Paperback | 34 pages
  • 189 x 246 x 2mm | 82g
  • United States
  • English
  • black & white illustrations
  • 1236895290
  • 9781236895295