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aberration according altitude argument arithmetical mean ascension and declination axes azimuth celestial sphere centre co-ordinates compute constant correction corresponding cos 8 sin cosine cosy cotang deduced denote determined Diff difference of longitude differential coefficients direction diurnal motion earth easily ecliptic equa errors of observation following equation formulae function given hence horizon hour angle instrument integral interpolation intersection interval latitude limb line of collimation logarithms lower culmination meridian method micrometer middle wire moon multiply numerical values nutation obliquity obtain order to find parallax parallel perpendicular plane pole positive axis precession prime vertical probable error probable values proper motion radius reading refraction residual errors right ascension screw side sidereal sine spherical squares star substitute subtract tables tang tang g telescope tion triangle true unknown quantities vernal equinox vernier vertical circle wire-cross zenith distance
Pàgina 375 - The cubes of the mean distances of the planets from the sun are proportional to the squares of their times of revolution.
Pàgina 105 - At the equator, as we have seen,* the days and nights are equal throughout the year — that is, they consist of 12 hours each ; but if we recede from the equator, north or south, this equality will cease to exist. When the sun is north of the equator the days are longer than the nights in the northern hemisphere ; and when the sun is south of the equator the reverse of this is the case; and in the southern hemisphere, of course, similar changes take place. At the equator the day is always 12 hours...
Pàgina 155 - This law states that the sine of the angle between the normal and the incident ray bears a constant ratio to the sine of the angle between the normal and the refracted ray; again all three directions are coplanar.
Pàgina 113 - The cause of this motion is shewn, by physical astronomy, to arise from the attraction of the sun and moon on the excess of matter at the equatoreal parts of the earth.
Pàgina 294 - Tables requisite to be used with the Nautical Ephemeris for finding the latitude and longitude at sea.
Pàgina 161 - Atmospheric currents, in high latitudes, when undisturbed, are westerly, particularly in the winter season. If storms and gales revolve by a fixed law, and we are able, by studying these disturbing causes of the usual atmospheric currents, to distinguish revolving gales, it is likely that voyages may...
Pàgina 3 - A cos 6 = cos a cos c + sin a sin c cos B cos c = cos a cos 6 + sin a sin 6 cos C Law of Cosines for Angles cos A = — cos B...
Pàgina 76 - ... ascensions are reckoned. This point may be considered as a star, though no star is, in fact, there; and, moreover, the point itself is liable to a certain slow variation, — so slow, however, as not to affect, perceptibly, the interval of any two of its successive returns to the meridian. This interval is called a sidereal day, and is divided into 24 sidereal hours, and these again into minutes and seconds. A clock which marks sidereal time, ie which goes uniformly at such a rate as always to...
Pàgina 131 - The Mean Obliquity of the Ecliptic at the beginning of the Year is taken 23°. 27'.