The American Ephemeris and Nautical Almanac

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Page 501 - Washington, by taking account of second differences. With greater longitudes of the place, the accuracy of the result obtained in this way will diminish. The columns of sidereal time of semidiameter passing meridian, etc., do not seem to need any explanation, except that they all refer to the moment of transit. The column Bright Limbs is given to indicate to the observer which limbs are illuminated. When two opposite limbs are both so nearly full that they can be well observed, both are indicated;...
Page 502 - Greenwich mean time: the fraction of the hour may be determined by dividing the hour propor tionally to the space which it represents on the map. This division may be a little more exact by allowing for the changes in this space as indicated by their varying width. The Greenwich mean time thus found must be reduced to local mean time by applying the longitude. As an example, suppose we wish to find the time at which the eclipse of 1893, Oct. 9, begins and ends at San Francisco, Cal. For the beginning...
Page 494 - The sun's declination is required for finding the latitude of the place, the local time, and the sun's azimuth and amplitude, from observations of the sun. The equation of time is needed in finding the mean time from observations of the sun, and the latitude from observations out. of the meridian.
Page 496 - Page IV contains The Moon's Semidiameter and Equatorial Horizontal Parallax, for each mean noon and midnight at Greenwich. Columns adjoining those of the horizontal parallax give the change of this quantity in one hour, by means of which it can be reduced to any other Greenwich mean time, in the same way as the sun's declination and the equation of time in the preceding examples. The sign plus or minus prefixed to the hourly differences, shows whether (he horizontal parallax is increasing or decreasing.
Page 502 - In the case of total and annular eclipses, a rough estimate of the magnitude of the eclipse may be obtained from the position of the place relatively to the central line and to the limit. On the central line, the eclipse is annular or total, while on the limit, the limb of the moon only grazes that of the sun. More Accurate Computations.
Page 496 - When great precision is needed, the hourly differences should be first interpolated for half the interval of Greenwich time from noon or midnight, and a correction applied to the horizontal parallax for the latitude of the place of observation. The Mean Time of the Moon's Upper Transit at Greenwich, which is given on page IV to...
Page 501 - Washington exceed those given in the column Mean Time of Transit, supposing the rate of change to be uniform and equal to what it is at the moment of transit over the meridian of Washington.
Page 493 - It will always be well to make the calculation by both methods, as their agreement will show both to be right. ‘ At sea it is ordinarily sufficient to have the declination to the nearest half minute, and the reduction may be found by Table V of BOWDITCH'S American Practical Navigator.
Page 491 - ... is called Solar Time. This is the most natural and direct measure of time. But the intervals between the successive returns of the sun to the same meridian are not exactly equal, owing to the varying motion of the earth around.

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