The Nautical Almanac and Astronomical Ephemeris for the Year ...order of the Lords Commissioners of the Admiralty, 1842 |
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Common terms and phrases
Aldebaran W Antares a Aquila Antares E Antares Saturn Antares SUN Apparent Declination Apparent Noon Apparent Right Ascension Aquarii Aquila E Aquila Saturn Arietis E ASCENSION AND DECLINATION Cancri Capricorni d h m Earth ECLIPSES Equation Fomalhaut E Frid FRIDAY Geminor Geocentric Greenwich Mean Greenwich Transit Heliocentric Hour of Long inverting telescope Jupiter E Leonis Libræ Logarithm LUNAR DISTANCES Mars Jupiter Mean Noon Meridian Longitude Meridian of Greenwich MONDAY Month Moon I. L. MOON'S RIGHT ASCENSION Name and Position NAUTICAL ALMANAC Ophiuchi P. L. of diff Pegasi E Piscium Point of Aries Pollux W R. A. Dec Regulus E Right Asc Sagittarii SATELLITES OF JUPITER SATURDAY Saturn E Scorpii Semi Semidiam Spica mg Spica my Antares Star's Name SUNDAY Tauri Thur THURSDAY TRANSIT AT GREENWICH True Dist Tues TUESDAY Variation of Right Vect Venus SUN Virginis WEDNESDAY white circle XVIII
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Síða 567 - The Equation of Time is the difference between Apparent and Mean Time, and therefore serves for the conversion of either time into the other. The numbers here given, show, for Greenwich Apparent Noon, the distance of the mean Sun from the meridian, or the portion of time to be added to, or subtracted from, (according to the precept at the head of the column,) Greenwich Apparent Noon to obtain the corresponding Mean Time at the same meridian, or the time which ought to be shown by the Mean Time Clock.
Síða 583 - Earth in its orbit, causes the Sun to appear in a different position from that which he really occupies, the true position being always in advance of the apparent. The numbers in...
Síða 586 - The hours and minutes of Right Ascension, and the degrees and minutes of Declination, are placed at the heads of the columns as constants, and belong equally to all the numbers below them. This arrangement has rendered it necessary, in numerous instances, to continue the seconds beyond 6o, as the width of the page would not permit of otherwise indicating any change in the minutes.
Síða 565 - Hence it is that astronomers, with a view of obtaining a convenient and uniform measure of time, have recourse to a mean solar day, the length of which is equal to the mean or average of all the apparent solar days in the year. An imaginary Sun, called the
Síða 582 - December 37 for the sake of convenience. This inclination is ever varying, as well from the effect of its mean diminution, as of the nutation of the earth's axis : it is an important element in deducing the positions of...
Síða 110 - THE TRANSITS OF THE SATELLITES AND THEIR SHADOWS OVER THE DISC OF THE PLANET.
Síða 577 - Emersion (Em.) the instant of its reappearance at coming out of the shadow. They generally happen when the Satellite is apparently at some distance from the body of Jupiter, except near the opposition of Jupiter to the Sun, when the eclipse takes place near to the body of the planet.
Síða 109 - THE SATELLITES OF JUPITER are not visible this Month, JUPITER being too near to the SUN. From Mean For correcting the Places of the Fixed Stars. 0...
Síða 574 - Lunar Distance has been observed on the surface of the Earth, and reduced to the centre, by clearing it of the effects of parallax and refraction, the numbers in the« pages enable us to ascertain the exact Greenwich mean time at which the objects would have the same distance.
Síða 565 - Astronomers, with the view of obtaining a convenient and uniform measure of time, have recourse to a mean solar day, the length of which is equal to the mean or average of all the apparent solar days in a year. An imaginary Sun, called the mean Sun, is conceived to move uniformly in the Equator with the real Sun's mean motion in Right Ascension, and the interval between the departure of any meridian from the main Sun and its succeeding return to it is the duration of the mean solar day.