The Practice of Navigation and Nautical Astronomy

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R.B. Bate, 1840 - Nautical astronomy - 330 pages

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Page viii - This is the more important, as very indistinct and erroneous notions prevail among practical persons on the subject of accuracy of computation ; and much time is, in consequence, often lost in computing to a degree of precision wholly inconsistent with that of the elements themselves. The mere habit of working invariably to a useless precision, while it can never advance the computer's knowledge of the subject, has the unfavourable tendency of deceiving those who are not aware of the true nature...
Page 260 - It is found, in general, that the tide is not due to the moon's transit immediately preceding, but to a transit which has occurred some time before. The time thus elapsed between the transit at which the tide originated and the appearance of the tide itself is called the retard, or age of the tide.
Page 94 - F, thick fog. g. Gloomy, dark weather. h. Hail. • 1. Lightning, m. Misty, hazy atmosphere. o. Overcast ; the whole sky being covered with an impervious cloud, p. Passing temporary showers, q. Squally. r. Rain ; continued rain, я. Snow, t. Thunder. u. Ugly, threatening appearance of the weather.
Page vi - ... the place of the ship, is extreme brevity of solution. It is not, however, merely as a concession to indolence, that rules should be made as easy and simple as possible; the nature of a sea life demands that every exertion should be made to abridge computation, which has often to be conducted in circumstances of danger, anxiety, or fatigue.
Page 228 - Almanac; the remainder is the prop. log. of a portion of time to be added to the time from the Nautical Almanac.
Page 172 - ... and which is thence called the Reduction to the Meridian." " This method is, in point of simplicity, but little inferior to the meridian altitude, to which it is next in importance ; and it particularly demands the attention of seamen, because, when the latitude by observation is left, as it too generally is, to the casualty of obtaining the meridian altitude, it is frequently lost for the day." " The term
Page 108 - For the same body the semidiameter varies with the distance; thus, the difference of the sun's semidiameter at different times of the year is due to the change of the earth's distance from the sun; and similarly for the moon and the planets.
Page 94 - Hail. 1 — Lightning. m — Misty hazy atmosphere. o — Overcast ; the whole sky being covered with an impervious cloud. p — Passing temporary showers. q — Squally. r — Rain ; continued rain. s — Snow. t— Thunder. u — Ugly threatening appearance of the weather.
Page 109 - A' in S. decl., fig. 2, is PA', which is the sum of 90 and A'B. 444. The AZIMUTH of a celestial body is the angle at the zenith contained between the meridian of the place of the spectator and the circle of altitude passing through the body. It is reckoned to begin from that part of the meridian which is on the polar side of the zenith, that is, from the N. in north latitude ; thus, the angle PZA is the azimuth of A. The angle MZA is the supplement of the azimuth to 180. This is often used for...
Page 2 - RULE. Multiply as in whole numbers, and point off as many decimal places in the product as there are decimal places in the multiplicand and multiplier, supplying the deficiency, if any, by prefixing ciphers.

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