Navigation and Nautical AstronomyD. Van Nostrand Company, 1919 - 259 pages |
Autres éditions - Tout afficher
Navigation and Nautical Astronomy John Huntington Crane Coffin,Elmer Beauchamp Collins Aucun aperçu disponible - 2018 |
Expressions et termes fréquents
angle apparent noon artificial horizon astronomical azimuth Azimuth Tables Bowd Bowditch celestial body celestial sphere chart Chro chronometer chronometer correction chronometer fast compass course computed Corr corresponding cosec difference of longitude east Ephemeris equal altitudes error EXAMPLE Find the latitude formula given Greenwich mean haversine formula heavenly body height of eye hour hour-angle instant instrument interpolated interval Jupiter L₁ line of position magnetic mean noon mean sun measured meridian altitude method moon moon's navigator observed altitude parallax parallel of latitude perpendicular plane Plane Sailing polar distance Polaris pole prime vertical reduce refraction rhumb-line right ascension Sailing semidiameter sextant altitude sidereal Solution stars subtractive SUMNER LINE sun's lower limb tion transit true altitude true course tude vernal equinox vessel vessel's position watch zenith distance ΙΟ
Fréquemment cités
Page 68 - Sun, and other fundamental astronomical data for equi-distant intervals of Greenwich mean time. Part II, Ephemeris for the Meridian of Washington, gives the ephemerides of the fixed stars, sun, moon, and major planets for transit over the meridian of the old Naval Observatory, Washington.
Page 2 - It is measured also by the arc of the horizon intercepted between the north or south point, and the foot of this vertical.
Page 228 - HWF & C."); for since, on such days, the moon's two transits (upper and lower) over the meridian occur about midnight and noon, the vulgar establishment then corresponds closely with the local times of high water. When more extended observations have been made, the average of all high water lunitidal intervals for at least a lunar month is taken to obtain what is termed, in distinction to the vulgar establishment, the corrected establishment of the port, or mean high water lunitidal interval. In...
Page 228 - RANGE. — The range of the tide is the difference in height between low water and high water. This term is often applied to the difference existing under average conditions, and may in such a case be designated as the mean range or mean rise...
Page 227 - ... simply the establishment. This interval is frequently spoken of as the time of high water on full and change days (abbreviated ' HWF & C.') ; for since, on such days, the moon's two transits (upper and lower) over the meridian...
Page 17 - Two BEARINGS OF A KNOWN OBJECT. — This is a most useful method, which is frequently employed, certain special cases arising thereunder being particularly easy of application. The process is to take a careful bearing and at the same moment read the patent log; then, after running a convenient distance, take a second bearing and again read the log, the difference in readings giving the intervening run; when running at a known speed, the time interval will also afford a means for determining the distance...
Page 3 - Angle of any point is the angle at the pole between the meridian of the observer and the hour circle passing through that point; it may also be regarded as the arc of the equinoctial intercepted between those circles.
Page 10 - To observe the altitude of a celestial body with the sextant and artificial horizon. — The artificial horizon is a small rectangular shallow basin of mercury, over which is placed a roof, consisting of two plates of glass at right angles to each other, to protect the mercury from agitation by the wind. The mercury affords a perfectly horizontal surface which is at the same time an excellent mirror.* If MN (Fig. 21) is the horizontal surface of the mercury, SB a ray of light from a star, incident...
Page 9 - Tho sextant is an instrument for measuring the angle between two objects by bringing into coincidence at the eye of the observer rays of light received directly from the one and by reflection from the other, the measure being afforded by the inclination of the reflecting surfaces. By reason of its small dimensions, its accuracy, and, above all, the fact that it does not require a permanent or a stable mounting but is available for use under the conditions existing on shipboard, it is a most important...
Page 228 - ... high water, full and change ; ' calculations based upon the former will more accurately represent average conditions, though the two intervals seldom differ by a large amount. " Having determined the time of high water by applying the establishment to the time of moon's transit, the navigator may obtain the...