The practice of navigation and nautical astronomy. [With] Tables [and] Supplement to the first ed1840 |
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The Practice Of Navigation And Nautical Astronomy. [with] Tables [and ... Henry Raper No preview available - 2019 |
The Practice Of Navigation And Nautical Astronomy. [with] Tables [and ... Henry Raper No preview available - 2022 |
Common terms and phrases
2d diff add add alter altitude alts angle apparent azimuth bearing Buncrana Cape Capt Castle celestial body centre chron chronometer CHRONOMETRIC DIFFERENCES circle Coast compass correction course Cruz decl declin deduced determined DIFFERENCES OF LONGITUDE dist distance diurnal motion East employed equator Funchal globe Goonung Greenwich Date horizon hour-angle insert interval La Guayra latitude longitude MARITIME POSITIONS mean measured meridian mole motion N.W. extr N.W. pt Naut navigators nearly North observation Observatory paragraph Parallel Sailing peak Pedra Branca plane plane sailing Port Jackson Port Mulgrave Port Royal prime vertical Pulo Condore reckoned refraction Replace rhumb line RIGHT ASCENSION rock S.E. pt sailing sextant ship shoal sidereal Sierra Leone sine South star subtract sun's supposed Table vertical West ΙΟ
Popular passages
Page 10 - The distance between two points on the surface of a sphere is the length of the minor arc of a great circle between them.
Page 9 - Long, much greater than itself; and thus increases the error of the Mer. Diff. Lat. in the same proportion. Thus, for example, at the course 80° the D. Long, exceeds the Mer. Diff. Lat. in the proportion of 6 to 1 ; at the course 85° this proportion is 11 to 1. Now when the course is large a slight change in it sensibly affects the D. Lat., and also the Mer. Diff. Lat., which is deduced directly from it.
Page 3 - STEAM NAVIGATION : Vessels of Iron and Wood ; the Steam Engine ; and on Screw Propulsion.
Page 9 - W. the Dep. is nearly the same as the distance, and an error of some degrees in the course does not affect the Dep. sensibly ; hence in this case the error of the D. Long, depends on that of the Dist. alone. But in Mercator's Sailing, on the other hand, we convert the Mer.
Page 8 - Long, deduced by Mid. Lat. sailing is too small ; an estimate of the error for places on the same side of the equator may be formed by the help of a few cases. Suppose the course 4 points or 45°, and the D. Lat. 10° or 600 miles ; then if this D. Lat. is made good in any latitude below 30° the error of the D. Long, will not exceed 2'; if made good between the parallels of 40° and 50° the error will be about 3' ; and between 60° and 70°, about 19', or £ of a degree.
Page 5 - DIST. 55-0 miles; LAT. IN 43°I7'N. 3. Current Sailing. •290. A current is named after the point towards which it runs or sets: thus, a current setting towards SE is called a south-east current. The mode adopted in speaking of the wind, which i<s named according to the point from which it blows, is thus reversed in speaking of a current.^ The term set, which is used to describe the direction of the current, is employed in the same way as in taking a bearing (No. 201) ; but it is necessary for the...
Page 9 - Dep. in a proportion which is less than 2 to 1 in all latitudes below (JO*, and exceeds 3 to 1 in latitudes beyond 70°. The error of the Dep., increased in the same proportion, becomes thus the error of the D. Long. Now when the course is nearly E. or W. the Dep. is nearly the same as the distance, and an error of some degrees in the coursedoes...
Page 26 - ... removed by taking all observations, including that for index-error, with the same motion of the index-bar. The onward motion being adopted as the most natural, the tangent-screw is always employed to close the object and the reflected image, and is thus always turned in the same direction. § One-fourth of the sum of the two readings should be equal to the sun's semi-diameter in the Nautical Almanac. This affords a test of the accuracy with which the observation has been made. 497. The adjusting...
Page 10 - ... of a semicircle about a diameter. A radius of the sphere is a line drawn from the centre to any part of the surface. A diameter is a line passing through the centre, and terminated at both ends by the surface. The circumference is the same as the circumference of a circle whose plane passes through the centre of the sphere. Such a circle is called a great circle. V. A segment of a sphere is a part cut off by any plane. The height of the segment is a perpendicular from the middle of the base to...
Page 12 - The student can easily supply a figure. (2.) To find the distance when the first bearing was taken. Enter the , Table with the supplement (or difference from 16 points) of the second number of points at the top, and the supplement of the first number of points at the side ; take out the multiplier, and proceed as above directed. Ex.