For example, if the right ascension of a star is exactly 15°, it will pass the meridian one sidereal hour after the vernal equinox.
We perceive then that the fundamental problems of sidereal science are closely linked up with the elementary and indispensable procedures of celestial measurement.
Among the most representative are: the Popular Science Monthly, New York; the monthly Boston Journal of Education; the quarterly American Journal of Mathematics, Baltimore; the monthly Cassier's Magazine (1891), New York; the monthly American Engineer (1893), New York; the monthly House and Garden, Philadelphia; the monthly Astrophysical Journal, commenced as Sidereal Messenger (1882), Chicago; the monthly American Chemical Journal, Baltimore; the monthly American Naturalist, Boston; the monthly American Journal of the Medical Sciences, Philadelphia; the monthly Outing, New York; the weekly American Agriculturist, New York; the quarterly Metaphysical Magazine (1895) New York; the bi-monthly American Journal of Sociology, Chicago; the bi-monthly American Law Review, St Louis; the monthly Banker's Magazine, New York; the quarterly American Journal of Philology (1880), Baltimore; the monthly Library Journal (1876), New York; the monthly Public Libraries, Chicago; Harper's.
The synodical revolution of the moon laid down the lines of the solar, its sidereal revolution those of the lunar zodiac. The first was a circlet of " full moons "; the second marked the diurnal stages of the lunar progress round the sky, from and back again to any selected star.
Of these the more noteworthy dealt with the distribution of stars, starclusters and nebulae, and the construction of the sidereal universe.
He founded the Sidereal Messenger in 1846, was one of the first to adopt (in 1848) the electrical method of recording observations, and published besides other works, The Orbs of Heaven (1848, &c.), and Popular Astronomy (1860), both reissued at London in 1892.
Days are distinguished as solar, sidereal or lunar, according as the revolution is taken relatively to the sun, the stars or the moon.
If the local sidereal time of the observation is known, the right ascension of the star becomes known by adding the observed hour angle to the sidereal time if the star is west of the meridian, or subtracting it if east of the meridian.
The eye end presents an refractor appearance too complicated to be figured here; it has a micrometer and its illumination for the position circle, a micrometer head, and a bright or dark field, clamps in right ascension and declination and quick and slow motion in the same, a finder, microscopes for reading the hour and declination circles, an illuminated dial showing sidereal time and driven by an electric current from the sidereal clock, and counter weights which can be removed when a spectroscope or other heavy appliance is added.
With the development of observational astronomy the sidereal universe was arbitrarily divided into areas characterized by special assemblages of stars; these assemblages were named asterisms by Ptolemy, who termed the brightest stars "of the fi rst magnitude," and the progressively fainter Stars.
We now arrive at the greatest of all the problems of sidereal astronomy, the structure and nature of the universe as a whole.
Hence if the earths axis of rotation deviates slightly from the axis of figure, it should describe a cone about the latter in 320 sidereal days.
In astronomical practice is introduced a day, termed " sidereal," determined, not by the diurnal revolution of the sun, but of the stars.
The latter are divided into sidereal hours, minutes and seconds as the solar day is.
15° for every sidereal hour of this interval.
Their sidereal year was 4zm too long, s and they kept the ecliptic stationary among the stars, making no allowance for the shifting of the equinoxes.
Hipparchus fixed the chief data of astronomy - the lengths of the tropical and sidereal years, of the various months, and of the synodic periods of the five planets; determined the obliquity of the ecliptic and of the moon's path, the place of the sun's apogee, the eccentricity of his orbit, and the moon's horizontal parallax; all with approximate accuracy.
Sidereal inquiries, as such, made no part of the original programme in which the stars figured merely as points of reference.
These were incidental trophies; Herschel's main object was the exploration of the sidereal heavens.
But thin amount of knowledge, however valuable in itself, is utterly inadequate to the needs of sidereal research; and various.
For the investigation of the general scheme of sidereal structure, the multiplication of results of the kind is indispensable.
The terms synodical, sidereal, tropical, anomalistic, nodical, are applied respectively to these months, of which the lengths are as follow: - N This diagram is a key to some of the features reproduced in the photograph.
The anomalistic month is the mean time taken by the moon in passing from one perigee to the next; the sidereal month is the mean time in which the moon makes a circuit among the stars; the tropical month is the mean time in which the moon traverses 360° of longitude; the nodical or draconic month is the mean time taken by the moon in passing from one rising node to the next; the solar month is one-twelfth of a tropical year.
The lengths of the various months are: synodic = 29.53059 days; anomalistic = 2 7.554 60, sidereal = 27 32166, tropical = 27.32156, nodical = 27.21222, solar= 30.43685.
Kugler 7 that the various periods underlying their lunar predictions were identical with those heretofore believed to have been independently arrived at by Hipparchus, who accordingly must be held to have borrowed from Chaldaea the lengths of the synodic, sidereal, anomalistic and draconitic months.
While sharing the opinion of Tycho as to the origin of such bodies by condensation of nebulous matter from the Milky Way, he attached a mystical signification to the coincidence in time and place of the sidereal apparition with a triple conjunction of Mars, Jupiter and Saturn.
Owing to the precession of the equinoxes it is longer than a tropical or sidereal year by 25 minutes and 2.3 seconds.
It is content to explain the origin and course of development of the world, the solar or, at most, the sidereal system which falls under our own observation.