A Treatise on Navigation and Nautical Astronomy: Including the Theory of Compass Deviations, Prepared for Use as a Text-book at the U. S. Naval AcademyUnited States Naval Institute, 1906 - 718 Seiten |
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12 hours apparent noon applied April April 26 astronomical azimuth bearing Bowditch celestial chro chronometer circle column compass Corr correction corresponding cosec course and distance curve d₁ D₂ declination departure deviation Diff difference of latitude difference of longitude dygogram earth East equation equinoctial error force formula G. A. noon given Greenwich mean heavenly body Height of eye horizon hour angle instant interval L₁ L₂ Long longitude lower limb magnetic mean sun Mercator chart meridian altitude method middle latitude miles minutes minutes of arc moon moon's Nautical Almanac navigator needle North observation parallax parallel parallel sailing plane prime vertical quadrantal refraction right ascension semi-diameter sextant sextant altitude ship ship's head sidereal sight sin² soft iron star sun's tangent tion transit triangle true altitude tude vernal equinox vernier West zero
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Seite 343 - Mean Solar Day is the interval between two successive transits of the mean sun over the same meridian ; it begins when the mean sun is on the meridian.
Seite 175 - ... of suspension may be measured by a scale on the glass cover. There is a small glass window in each end provided with an index line to mark the horizontal plane. Without the small weight, the needle before being magnetized was exactly balanced, so the weight is intended to balance the vertical magnetic force ashore or on board. If a...
Seite 68 - ... distance must depend on the range the ship takes when swinging ; if she be at anchor, in a tide-way, from 6 to 8 miles is not too much ; brought up by the middle (in a dock) 2 miles will suffice. 239. The next step is to determine the correct magnetic bearing of the selected object from the ship ; or in other words, the compass bearing it would have from on board if it were not disturbed by the attraction of the iron in the ship. This is effected by taking the compass to some place on...
Seite 304 - Fig. 1002, let the sextant be held vertically and let a be the index glass after the index arm ad has been turned so that the index glass is parallel to the horizon glass b and the index d coincides with the zero of the limb. A ray of light...
Seite 555 - The transmitting clock that sends out the signals is corrected very accurately, shortly before noon, from the mean of three standard clocks that are rated by star sights with a meridian transit instrument. The noon signal is seldom in error to an amount greater than one or...
Seite 360 - Moon's Semidiameter and Equatorial Horizontal Parallax for each mean noon and midnight at Greenwich. Columns adjoining those of the horizontal parallax give the change of that quantity in one hour, by means of which it can be reduced to any other Greenwich mean time, in the same way as the Sun's declination and the equation of time in the preceding examples. The...
Seite 45 - ... used, though not indicated on the card. A system of numbering the degrees from 0° to 360°, always increasing toward...
Seite 486 - These are modifications of the fundamental formula: sin h = sin L sin d + cos L cos d cos t, which is itself often preferred for the computation of the altitude from the latitude, declination, and hour angle.
Seite 291 - ... force depends on this inclination, the amount of precession due to the action of the moon has a period equal to one revolution of the moon's node, or 18-6 years. These inequalities in the motion of precession are termed nutation. Changes in the Right Ascensions and Declinations of the Stars. — Since the declination of a heavenly body is its angular distance from the celestial equator, it is evident that any change in the position of the equator must change the declinations of the fixed stars....
Seite 288 - Latin meridies, mid-day), is a great circle of the celestial sphere, passing through the poles of the earth and the zenith and nadir, crossing the equator at right angles, and dividing the sphere into an eastern and western hemisphere.