The Whys and Wherefores of NavigationD. Van Nostrand, 1918 - 163 pages |
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Common terms and phrases
24 hours amount aphelion apparent sun astronomical axis azimuth bearing becomes Bowditch calculated celestial equator celestial pole celestial sphere chronometer circle of equal clock compass error correction corresponding course dead reckoning declination deviation diagram difference of longitude direction diurnal earth east or west eastward equal altitude fixed stars Greenwich mean heavenly bodies heavens intersection interval light line of position March 21st mariner mean sun measured Mercator chart meridian altitude method miles moon moon's motion movement moving Nautical Almanac navigator noon north or south north pole northern observed altitude obtained parallax parallel perihelion plane Point of Aries polar posi position line practical precession prime vertical quadrant radius refraction result revolution right angles right ascension rotation sailing seen semi-diameter sextant ship ship's position side sidereal sight solar day subtracted sun's Table taken terrestrial ecliptic tion triangle tude variation vernal equinox vessel westward zenith distance
Popular passages
Page 108 - ... made to preserve her position as nearly as possible until daylight; when nothing being in sight, she was kept on ENE under short sail, with heavy gales; at about 10 AM an altitude of the sun was observed, and the Chronometer time noted; but, having run so far without any observation, it was plain the Latitude by dead reckoning was liable to error, and could not be entirely relied on. "Using, however, this Latitude, in finding the Longitude by Chronometer, it was found to put the ship 15
Page 61 - June 21st that part of the equation of time due to the obliquity of the orbit bears a minus sign when mean time is desired from the apparent time.
Page 107 - Greenock, a series of heavy gales from the westward promised a quick passage ; after passing the Azores, the wind prevailed from the southward, with thick weather; after passing longitude 21° W., no observation was had until near the land ; but soundings were had not far, as was supposed, from the edge of the bank. The weather was now more boisterous, and very thick ; and the wind still Southerly; arriving about midnight, 17th December, within 40...
Page 108 - The deduction followed that, though the absolute position of the ship was doubtful, yet the true bearing of the Smalls light was certain, provided the chronometer was correct. The ship was therefore kept on her course, ENE, and in less than an hour the Smalls light was made bearing E. by N. i N. and close aboard. The latitude by DR turned out to be 8
Page 12 - Azimuth of a star is the angle at the zenith formed by the meridian of the observer and the vertical circle passing through the star, and is measured therefore by an arc of the horizon.
Page 108 - Tusker light; the wind hauled SE, true, making the Irish coast a lee shore; the ship was then kept close to the wind, and several tacks made to preserve her position as nearly as possible until daylight; when nothing being in sight, she was kept on ENE under short sail, with heavy gales; at about 10 AM an altitude of the sun was observed, and the Chronometer time noted; but, having run so far without...
Page 14 - The prime meridian of this system passes through the intersection of the celestial equator, and the ecliptic — the vernal equinox or First Point of Aries.
Page 107 - December, within 40 miles, by dead reckoning, of Tuskar light, the wind hauled SE. true, making the Irish coast a lee shore; the ship was then kept close to the wind and several tacks made to preserve her position as nearly as possible until daylight, when, nothing being in sight, she was kept on ENE. under short sail with heavy gales. At about 10 am an altitude of the sun was observed and the chronometer time noted; but, having run so far without...
Page 50 - The hour angle of a body is the angle formed at the pole between the meridian and the hour circle passing through the body measured westward.