## Navigation and nautical astronomy, Volume 1 |

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### Common terms and phrases

24 hours altitude for index apparent altitude April 27 ascension mean sun celestial concave celestial equator chro chronometer on Greenwich chronometer showed compass bearing compass course cosec course and distance deviation diff difference of latitude dist east Elements from Nautical equation given Greenwich date Greenwich mean noon haversines heavenly body height of eye horizontal parallax hour-angle Index cor index correction June latitude and longitude mean time nearly miles moon Moon's semi moon's semidiameter Nautical Almanac observed altitude observed meridian altitude p.m. mean parallel sailing plane plane sailing polar distance proportional logarithm required the latitude required the longitude required the true required the variation right ascension Rule sailed sextant ship mean ship's head sidereal star subtract Sun's declination sun's L. L. sun's lower limb T. D. lat true altitude true bearing true course true difference true distance vers versine zenith distance

### Popular passages

Page 67 - The right ascension of a heavenly body is the arc of the equator, intercepted between the first point of Aries and the circle of declination passing through the...

Page 68 - The longitude of a heavenly body is the arc of the ecliptic intercepted between the first point of Aries and the circle of...

Page 18 - CAD=67° 30', the supplement of the angle subtended by the other two points в and с : produce the lines AD and CD to meet in the point D. About the triangle ADC describe a circle ; then the place of the reef will be somewhere in the circumference of this circle. To find it, join BD; and the point of intersection G is the position of the reef required. For since the angles in the same segment of a circle are equal (Euclid, b. iii.), therefore AQD=ACD=63° 20'; therefore the angle AGB=116° 40'....

Page 22 - Fig. 3) loaded on the circular side with lead sufficient to make it swim upright in the water: to this is fastened a line about 150 fathoms long, called the Log-line, which is divided into certain spaces called knots, and is wound on a reel (see Plate VI.

Page 143 - On this account it is usual to apply to the first altitude a correction so as to reduce it to what it would have been if taken at the place of the second observation ; this quantity is called i: the correction for run of the ship," and may be calculated us follows.

Page 65 - ... path of the sun as seen from the Earth, and is called the Ecliptic. The plane of the Earth's equator, extended till it meets the concave surface of the heavens, forms what is called the Celestial Equator, or the Equinoctial. The ecliptic and the equinoctial form an angle of 23° 28', and this angle is called the Obliquity of the Ecliptic. The axis of the Earth, therefore, instead of being perpendicular to the plane of its orbit, is inclined to it at an angle of (90° — 23° 28') 66° 32'.

Page 67 - ... once through the two principal fixed points, the pole and the zenith. It divides the visible hemisphere into two regions on the right and left of the observer; as he looks to the north, that which is on his right being called the EASTERN, and that which is on his left the WESTERN. Another vertical at right angles to the meridian is called the PRIME VERTICAL. This is comparatively little used for reference. 2343. Cardinal points. — The meridian and prime vertical divide the horizon at four points,...

Page 68 - The hour angle of a heavenly body is the angle at the pole between the celestial meridian and the circle of declination passing through the place of the body : thus ZPX is the hour angle of X.

Page 68 - 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.

Page 246 - October 9? 4. September 27, 1878, in long. 101° E. the observed meridian altitude of the sun's LL was 47° 26' 50" (zenith S. of the sun), the index correction was + 2' 40", and the height of the eye above the sea was 15 feet; required the latitude.