Training Manual [2000-]. |
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Common terms and phrases
alidade altitude method apparent solar astronomic triangle azimuth mark azimuth of Polaris celestial body celestial equator celestial pole celestial sphere Correction for longitude cross wires declination earth east or west eastern elongation Ephemeris error field notes Greenwich mean horizontal angle horizontal verniers hour circle hour-angle method instant latitude local apparent Longitude west lower culmination main telescope Mean angle mean solar civil mean sun Mean time interval MERIDIAN DETERMINATION minutes motion observed altitude Oh local mean paragraph 23 parallax plane plumb line polar axis polar distance positions prime vertical record the readings right ascension set of readings sidereal day sidereal hour angle sidereal interval sight the azimuth spherical angle Standard 75th meridian standard time meridian star at elongation station Subtract Table TOPOGRAPHY AND SURVEYING Unclamp the upper upper culmination upper horizontal plate upper transit Variation for longitude vernal equinox vertical circle watch west of north
Popular passages
Page 30 - ... to coincide with the vertical hair. Then mark the point directly under the theodolite ; the line passing through this point and the staff, makes an angle with the true meridian equal to the azimuth of the pole-star. From the table of azimuths, take the azimuth corresponding to the year and nearest latitude. If the observed elongation...
Page 11 - A sidereal day is the interval of time between two successive upper transits of the vernal equinox over the same meridian.
Page 7 - The obliquity of the ecliptic is the angle between the plane of the equator and the plane of the ecliptic. The angle is not absolutely constant, but is subject to slight periodic changes ; it is approximately 23° 2/.
Page 14 - If the mean time of upper culmination is not known, the time of either elongation may be determined as follows: To the sidereal hour angle of the star add the right ascension of the star. The result is the sidereal hour angle of the vernal equinox or the right ascension of the meridian or the sidereal time at elongation, all of which amount to the same thing.
Page 19 - ... compass, the use of which does not depend on any astronomic principle, but simply on the magnetic attraction of the earth's mass. The magnetic needle, when allowed to swing freely, will come to rest in the magnetic meridian.
Page 10 - Therefore clocks cannot be regulated to apparent solar time. However, observations on the sun will give its hour angle ; add 12 hours to give apparent solar time. Mean Solar (Civil) Time. In order to establish a solar day of uniform length, a fictitious luminary called the mean sun is assumed to move uniformly in the celestial equator, completing the circuit in one tropical year.
Page 4 - The earth has several simultaneous motions, only two of which need be discussed here. The earth rotates from west to east on its polar axis once each day. This rotation produces day or night at a certain point on the earth, according as the point is toward or away from the sun. The earth also revolves in a counterclockwise direction (as viewed from the north) in an elliptical orbit around the sun, with the sun not at the center, but at one of the foci of the ellipse, making a complete circuit in...
Page 4 - The earth's axis of rotation is not perpendicular to the plane of its orbit but is inclined to it at an angle of 66° 33' — that is, the plane of the earth's Equator is inclined at an angle of 23° 27' to the plane of the earth's orbit.
Page 9 - Almanac, beginning with the volume for 1925, an apparent solar day at any place is the interval of time between two successive lower transits of the Sun over the meridian of that place, and the apparent solar time is the hour angle of the Sun plus 12 hours.
Page 7 - The equinoctial colure is the meridian passing through the equinoxes. The solstitial colure is the meridian passing through the solstices; the solstitial colure is a common secondary to the ecliptic and equator.