The American Ephemeris and Nautical Almanac

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Page 466 - The ephemeris time at any instant is obtained from observation by directly comparing observed positions of the sun, moon, and planets with gravitational ephemerides of their coordinates; observations of the moon are the most effective and expeditious for this purpose. An accurate determination, however, requires observations over a more or less extended period; in practice, it takes the form...
Page 492 - The longitude of the evening terminator differs by 180 from that of the morning terminator. The position angle of the axis is the angle that the lunar meridian through the apparent central point of the disk towards the north lunar pole forms with the declination circle through the central point, reckoned eastward from the north point of the disk. The column headed Position Angle—Bright Limb contains the position angles of the midpoint of the illuminated limb, reckoned eastward from the north...
Page 482 - the times at which the excess of the apparent longitude of the moon over the apparent longitude of the sun is 0, 90, 180, and 270, respectively.
Page 492 - The POSITION ANGLE of the AXIS is the angle that the lunar meridian through the apparent central point of the disk towards the north lunar pole forms with the hour circle through the central point, reckoned eastward from the north point of the disk.
Page iii - Beginning with the editions for 1960, The American Ephemeris and Nautical Almanac issued by the Nautical Almanac Office, United States Naval Observatory, and The Astronomical Ephemeris issued by HM Nautical Almanac Office, Royal Greenwich Observatory, were unified. With the exception of a few introductory pages, the two publications are identical; they are printed separately in the two countries, from reproducible material prepared partly in the United States of America and partly in the United Kingdom.
Page iv - Contains the ephemeris of Universal and Sidereal Times, the ephemerides of the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, the geocentric ephemerides of Ceres, Pallas, Juno, Vesta and Pluto, the nutation in longitude and obliquity, the Day Numbers, and the Phenomena. This volume also contains data on mean places of stars; eclipses of the Sun and Moon; ephemerides for physical observations of the Sun, Moon, and planets; ephemerides of the satellites of Mars, Saturn, Uranus,...
Page 466 - Ephemeris Time is the uniform measure of time defined by the laws of dynamics and determined in principle from the orbital motions of the planets, specifically the orbital motion of the Earth as represented by NEWCOMB'S Tables of the Sun.
Page 495 - System I applies to all objects situated on or between the north component of the south equatorial belt and the south component of the north equatorial belt. Month Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. UT GMAT 24...
Page 490 - The position angle P of the point of contact, reckoned from the north point of the limb of the Sun towards the east, may be taken as equal to its geocentric value given above.
Page 492 - When the libration in longitude, or selenographic longitude of the Earth, is positive, the mean central point of the disk is displaced eastward on the celestial sphere, exposing to view a region on the west limb. When the libration in latitude, or selenographic latitude of the Earth, is positive, the mean central point of the disk is displaced towards the south, and a region on the north limb is exposed to view. The selenographic coordinates of the point on the lunar surface where the Sun is in the...

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