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accuracy accurately angular apparent approximate astronomical astronomical transit azimuth bubble Cassiopeia celestial sphere centre chronometer circumpolar star computed constellations coordinates Corr culmination Decl declination determined difference earth east ecliptic elongation engineer's transit Ephemeris Equa equal altitudes equator equinox error Example formula given Greenwich Mean horizontal angle horizontal axis hour angle hour circle index correction instant instrument interpolation interval latitude line of sight longitude lower limb Mean Noon mean solar mean sun measured meridian method minutes moon moon's motion Nautical Almanac nearly necessary object Observed altitude observer's obtained orbit parallax perpendicular plane polar distance Polaris pole polestar position prime vertical refraction correction result right ascension rotation sec h seen semidiameter sidereal day sight line spirit level subtracting sun's Table tangent telescope tide tion triangle true tube tude upper variation per hour vertical arc vertical axis vertical circle zenith distance
Page 100 - Zodiac," are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces.
Page 20 - The hour angle of a point is the arc of the equator between the observer's meridian and the hour circle through the point. It is measured from the meridian westward (clockwise) from o* to 24* or from o° to 360°. In Fig. 16 the declination of the star S is AS (negative); the hour angle is M F1G.
Page 19 - The first coordinate of a point is its angular distance north or south of the equator, measured on an hour circle; it is called the Declination. Declinations are considered positive when north of the equator, negative when south. The complement of the declination is called the Polar Distance. The second coordinate of...
Page 189 - The astronomical day begins twelve hours after the civil day, ie, begins at noon on the civil day of the same date, and is reckoned from 0 to 24 hours. Consequently an astronomical time less than twelve hours refers to the same civil...
Page 189 - ... to 24 hours. Consequently an astronomical time less than twelve hours refers to the same civil day, whereas an astronomical time greater than twelve hours refers to the morning of the next civil day. It will be noticed that for the tabular year two eastern elongations occur on January 12 and two western elongations on July 12.
Page 40 - A solar day is the interval of time between two successive upper transits of the sun over the same meridian. The solar time at any instant is the hour angle of the sun at that instant.
Page 165 - In making the observation the instrument is set up at one end of the line whose azimuth is to be determined, and the plate vernier set at o°. The vertical cross hair is set on the mark and the lower clamp tightened. The sun glass is then put in position, the upper clamp loosened, and the telescope pointed at the sun. It is not necessary to observe on both edges of the...
Page 190 - ALPHA BETA GAMMA DELTA EPSILON ZETA ETA THETA IOTA KAPPA LAMBDA MU NU XI OMICRON PI RHO SIGMA TAU UPSILON PHI CHI PSI OMEGA...
Page 10 - While the direction of the earth's rotation axis is so nearly constant that no change is observed during short periods of time, there is in reality a very slow progressive change in its direction. This change is due to the fact that the earth is not quite spherical in form but is spheroidal, and there is in consequence a ring of matter around the equator upon which the sun and the moon exert a force of attraction which tends to pull the plane of the equator into coincidence with the plane of the...