The American Ephemeris and Nautical Almanac Volume 964 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1883 Excerpt: ...is chiefly used when the sun is observed on the meridian, and the local apparent lime is O-'oO." The longitude from Greenwich expressed in time, if west, is at that instant the Greenwich apparent time, or time after Greenwich apparent noon; if east, it is time before Greenwich apparent noon. The longitude of imy place is therefore employed in reducing the quantities on this page to apparent noon at the place. The right ascension of the sun thus reduced is the sidereal time of local apparent noon. The difference between it and the clock time of the meridian passage of the sun is the error of the clock on sidereal time. The declinat'on of the sun reduced to the meridian, or apparent noon, of the place, is required in finding the latitude from a meridian altitude of the sun. As an example of the use of page I: --Let the sun's declination be required at apparent noon, 1886, May 30, at a place whose longitude is 180 2C, or 12h lm 20 west from Greenwich. h m a Local apparent time.. May 30, 0 0 0 Longitude from Greenwich (adflitive) 12 I 20 Greenwich apparent time.. May 30, 1 Si 1 20 Reducing the minutes and seconds to decimals of an hour, we find that this moment is 12h.022 after Greenwich apparent noon on May 30, or llh.978 before Greenwich apparent noon on May 31. On page 74 of the Ephemeris we find that the change of declination in one hour is // May 30, at Greenwich apparent noon 22.14 May 31, at Greenwich apparent noon 21.19 Difference for one day..... 0.05 If we want to be very exact, we find the amount of this hourly difference for the time which is half way between Greenwich noon and the time of observation'; that is, for 6 hours after Greenwich noon of the 30th, this being half of 12 hours. Six hours is 0.25 of a day; so the calculation is as fo...