Tables for Azimuths, Great-circle Sailing, and Reduction to the Meridian, with a New and Improved "Sumner" Method: Latitudes 850 N. to 850 S., Declinations 850 N. to 850 S.: Also Other Useful Navigational Tables, with Numerous Examples of Double Altitudes, Equal Altitudes, Azimuths, Etc

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By authority: John Mackay, 1908 - Azimuth - 159 pages
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Page xii - ... to admit that the only means of inducing seamen generally to profit by the numerous occasions which offer themselves for finding the place of the ship, is extreme brevity of solution. It is not, however, merely as a concession to indolence, that rules should be made as easy and simple as possible ; the nature of a sea life demands that every exertion should be made to abridge computation, which has often to be conducted in circumstances of danger, anxiety, or fatigue...
Page xii - Those who have been brought up to the sea, and who have experienced the distaste for long calculations which that kind of life inspires, will not hesitate to admit that the only means of inducing seamen generally to profit by the numerous occasions which offer themselves for finding the place of the ship, is extreme brevity of solution. It is not, however, merely as a concession to indolence, that rules should be made as easy and simple as possible ; the nature of a sea life demands that every exertion...
Page 90 - E. : required error of compass ; and supposing the variation to be 15* 30' E. : required the deviation of the compass for the position of the ship's head at the time of observation. 9. 1882, December 24th, AM at ship, latitude 33
Page 150 - Altitudes," is credited with having Altitudes. said in the course of a lecture at Glasgow, " that it would be the greatest blessing to navigators, both young and old, if every other method of ordinary navigation could be swept away.
Page 4 - For converting INTERVALS of MEAN SOLAR Time into Equivalent INTERVALS of SIDEREAL Time.
Page 101 - ... was found. The following rules may indicate to the navigator the conditions under which caution must be observed, and the direction of probable error: (a) A displacement of the horizon should always be suspected when there is a marked difference between the temperatures of air and sea water; this fact should be especially kept in mind in regions such as those of the Red Sea and the Gulf Stream, where the difference frequently exists.
Page 64 - Let the latitude by account and the longitude thus obtained be corrected for the run of the ship in the interval between the observations, and let the second observation be worked with this corrected latitude. Name these longitudes (1) and (2). "III. The bearing ( true azimuth) of the sun at each observation is to be taken from an Azimuth Table.
Page 113 - APPROXIMATE APPARENT TIMES OF THE MERIDIAN PASSAGES OF THE PRINCIPAL FIXED STARS.
Page 49 - E. course during the interval between the observations. Required the line of position and true bearing of the sun at...
Page 84 - Then choose another star on the other side of the meridian, as near as possible the same distance from the meridian; calculate the longitude with the latitude found from the previous observations, and the true longitude will be obtained by taking the mean between the eastern and western stars worked with ihe correct latitude. Elimination of Errors in Altitude, Diagram showing how the true latitude may be found by the "Sumner" method even when altitudes have been observed by a sextant with large unknown...

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