The Nautical Almanac and Astronomical Ephemeris for the Year - Softcover
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. 1862 Excerpt: ...the portion of time to be added to or subtracted from, (according to the precept at the head of the column,) Greenwich apparent noon to obtain the corresponding mean time at the same meridian, or the time which ought to be shown by the mean time clock. 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 Jan. 16th, 1866, in longitude 450 or 3h East of Greenwich, to be 6h P.M. civil time, and it were required to convert it into mean time; subtracting the difference of longitude 3h from the apparent time at the place, we have Jan. 16, 311 for the corresponding astronoraical apparent time at Greenwich. The difference of the equation for i hour at January 16, oh or apparent noon is ©854, and at Jan. 17, oh it is o,-824, consequently, for midway between noon and 3h, or ih $6", it is o"-852, which multiplied by 3, gives 2,-556 for the variation in 3 hours, and this being added (because the equation is increasing) to iom 4'"88, the equation of time at apparent noon, the result is iom 7'"44, to be added (according to the precept at the head of the column) to the given apparent time 6h, whence we obtain 6h iom 7'44 for the mean time required. At page I. of the month of April, we observe, at the head of the column " which signifies that a change of precept occurs in the course of the month; and between the equations opposite to April 15 and 16, a black line, indicating that the change occurs between those days. The upper precept applies to all the quantities above the bla...
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- PublisherRarebooksclub.com
- Publication date2012
- ISBN 10 1236075072
- ISBN 13 9781236075079
- BindingPaperback
- Number of pages38
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