The Nautical Almanac and Astronomical Ephemeris for the Year 1838

The Nautical Almanac and Astronomical Ephemeris for the Year 1838

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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. 1835 edition. Excerpt: ...39"6, for the Declination required. The Semidiameter of the Sun. The numbers in this column express the angle at the centre of the earth subtended by the Suns Semidiameter, and are required foT reducing observations of the limb to the centre, as in the instance of measuring the altitude of the Suns upper or lower limb, or the distance of the Moon from the Sun. Equation of Time. The numbers in this column are the values of the equation at the instant of Mean Noon, and therefore serve more particularly to convert Mean into Apparent Time: for which purpose we have only to apply the equation according 12h be subtracted the equation 4m -51, the difference 11" 55m 58'49 is the corresponding apparent time. To find the equation of time at 10" P.M. mean time on April 15, 1838, in longitude 62, or 4h 8, West of Greenwich. Add the difference of longitude to the given time, because it is West, and the corresponding astronomical mean time at Greenwich is April 15d 14h 8m. The variation in 24 hours is 14-88, that is, the sum of the equations belonging to the noons of the 15th and 16th, because the equation has decreased to 0 and then increased in the interval, therefore 24h: 14-88:: 14h 8: 8-76, which, being greater than 0m 3 41, the equation on the 15th, which was decreasing, shows that in the 14h 8m the equation has passed through its state of decrease to zero, or 0, and is now increasing. The difference 5-35 is the equation of time at the time proposed, and is to be added to mean time, because it has passed the zero. Sidereal Time at Mean Noon is the angular distance of the First point of Aries, or the true Vernal Equinox, from the meridian, at the instant of Mean Noon: it is therefore the Right Ascension of the...show more

Product details

  • Paperback | 32 pages
  • 189 x 246 x 2mm | 77g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236771699
  • 9781236771698