The Suns Declination And Equation Of Time

Author : Great Britain Hydrographic Dept
Publisher : Forgotten Books
ISBN 13 : 9780656211166
Total Pages : 338 pages
Book Rating : 4.2/5 (111 download)

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Download or read book Sun's True Bearing, Or Azimuth Tables written by Great Britain Hydrographic Dept and published by Forgotten Books. This book was released on 2018-02-10 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Sun's True Bearing, or Azimuth Tables: Computed for Intervals of Four Minutes Between the Parallels of Latitude 30 and 60 ̊inclusive To the practical navigator, the ready determination of the Sun's true bearing or azimuth has always been deemed of great importance, but more especially will the advantage of tabular results be appreciated at the present time, when however carefully the compasses of an iron or steel-built ship may be corrected, so much depends upon frequent observations of the deviation under the varying conditions of a ship at sea. In the Azimuth Tables by Thomas Lynn, Commander in the late East India Company's Service, which were published in 1829, the Sun's altitude is the chief element involved for finding the azimuth, the time not being employed. In the following Azimuth Tables (for the zones between the parallels of 30 and 60 in both the time is the chief element employed, the azimuths being computed from the well-known problem in spherical trigono metry, viz. - two sides (co-lat. And pol. Dist.) and included angle (hour angle, which for the Sun is the apparent time from noon, ) being given, to find the angle at the zenith, which is the azimuth. The apparent time at ship is readily' determined by altitudes of the heavenly bodies, or it may be found, with sufficient accuracy for this purpose, by computing it from Greenwich mean time, the equation of time, and the longitude in time; Results exhibited in a tabulated form have certain advantages. In these tables, for example, the value of an error in either of the three elements used in the computation is seen at once, and hence the most desirable time for making the observations, so that an error in either the apparent time, latitude, or declination shall produce the least error in the true bearing. As greater dependence can be placed on the result when the magnetic bearing of the Sun or other heavenly body is observed at a low altitude, the azimuths in the following tables are not given when the altitude exceeds 60 degrees. Supplementary Tables are appended of the Sun's Declination and the Equation of Time; the latter table will be found convenient to vessels in port, provided with local time for reducing mean to apparent time. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.