## A Treatise on Nautical Astronomy: For the Use of Students |

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A Treatise on Nautical Astronomy: For the Use of Students (Classic Reprint) John Merrifield No preview available - 2016 |

### Common terms and phrases

apparent apparent altitude applied astronomical azimuth bearing calculated called celestial centre chronometer circle compass correction corresponding cosec declination deduced determining difference direction earth east equation Explain feet formula given gives greater Greenwich half heavenly body height hence horizon hour angle index error interval July known latitude length less limb Long longitude mean mean solar mean sun measured meridian method minutes moon moon's Nautical Almanac nearly noon object observed altitude obtained pass plane polar distance pole position reduced refraction Required result right ascension rising Royal Naval College rule semidiameter sextant ship ship's side sidereal slow star subtract sun's tables taken tion transit true true altitude variation vertical zenith distance

### Popular passages

Page 288 - Sun, the larger planets and certain stars as they would appear from the centre of the Earth. When a Lunar Distance has been observed on the surface of the Earth, and reduced to the centre, by clearing it of the effects of parallax and refraction, the numbers in these pages enable us to ascertain the exact Greenwich mean time at which the objects would have the same distance.

Page 141 - Observer' at a salary of 100£ per annum, his duty being 'forthwith to apply himself with the most exact care and diligence to the rectifying the tables of the motions of the heavens and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting the art of navigation.

Page 288 - ... in the Ephemeris; the remainder will be the proportional logarithm of a portion of time to be. added to the hour answering to the nearest distance, to obtain the approximate Greenwich mean time corresponding to the given distance.

Page 93 - Sidereal Time at Mean Noon is the angular distance of the first point of Aries, or the true vernal equinox, from the meridian, at the instant of mean noon : it is therefore the Right Ascension of the mean Sun, or the time which ought to be shown by a sidereal clock at Greenwich, when the mean time clock indicates oh om os.

Page 34 - An apparent solar day is the interval between two successive transits of the sun across the meridian.

Page 306 - ... these are known accurately. The last (the corrected distance between the Sun and the Moon) must be estimated. There is no difficulty in doing this with accuracy abundantly sufficient for this investigation. With Greenwich time by account, the distance may be rudely computed from the distances in the Nautical Almanac. Or, without time or calculation, a navigator accustomed to lunar distances may form a shrewd guess of the probable amount of correction. (The effect of a possible error will be exhibited...

Page 141 - Mathematical o>jgraphy.) the arc of the equator, intercepted between the first meridian...

Page 308 - C . cos. a . sin. 6 . cos. c _ — 2 . sin. A . sin. B . sin. C . sin. a . sin. b . sin. c I — 2 sin.

Page 35 - A Solar Day is the interval of time between two successive transits of the sun over the same meridian; and the hour-angle of the sun is called Solar Time.

Page 142 - Fourthly, that the conference recognizes for certain scientific needs and for the service for the great administrations of the means of communication, such as railways, steamship lines, telegraphs, and posts, the utility of adopting a universal hour, side by side with the local or national hours, which will necessarily continue to be employed in civil life. " Fifthly, that the conference recommends, as the point of departure of the universal hour and of cosmopolitan dates, the mean noon of Greenwich,...