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The planetary hours are an ancient system in which one of the seven classical planets is given rulership over each day and various parts of the day. Developed in Hellenistic astrology, it has possible roots in older Babylonian astrology, and it is the origin of the names of the days of the week as used in English and numerous other languages.
Sidereal time was defined such that the March equinox would transit the meridian of the observatory at 0 hours local sidereal time. [ 7 ] Beginning during the 1970s, the radio astronomy methods very-long-baseline interferometry (VLBI) and pulsar timing overtook optical instruments for the most precise astrometry .
Planetary hours This page was last edited on 7 May 2024, at 05:38 (UTC). Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional ...
The earliest known descriptions of planetary equatoria are in the Latin translation of an early eleventh century text by Ibn al‐Samḥ and a 1080/1081 [3] treatise by al-Zarqālī, contained in the Libros del saber de astronomia (Books of the knowledge of astronomy), a Castilian compilation of astronomical works collected under the patronage ...
Unequal hours were the result of dividing up the period of daylight into 12 equal hours and nighttime into another 12. There is more daylight in the summer, and less night time, so each of the 12 daylight hours is longer than a night hour. Similarly in winter, daylight hours are shorter, and night hours are longer.
Earth's LOD difference (ΔT) is slight, but the cumulative time discrepancy from the earliest accurately dated solar eclipses to the time this discrepancy was first noticed is several hours. Because of this difference, the positions of objects in the sky as viewed from a given point on Earth's surface remain uncertain before the beginning of ...
A sidereal year (/ s aɪ ˈ d ɪər i. əl /, US also / s ɪ-/; from Latin sidus 'asterism, star'), also called a sidereal orbital period, is the time that Earth or another planetary body takes to orbit the Sun once with respect to the fixed stars.
The Ptolemaic system of planetary spheres asserts that the order of the heavenly bodies from the farthest to the closest to the Earth is Saturn, Jupiter, Mars, Sun, Venus, Mercury, and the Moon; objectively, the planets are ordered from slowest to fastest moving as they appear in the night sky. [5]