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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.
For solid objects, such as rocky planets and asteroids, the rotation period is a single value.For gaseous or fluid bodies, such as stars and giant planets, the period of rotation varies from the object's equator to its pole due to a phenomenon called differential rotation.
More exactly, sidereal time is the angle, measured along the celestial equator, from the observer's meridian to the great circle that passes through the March equinox (the northern hemisphere's vernal equinox) and both celestial poles, and is usually expressed in hours, minutes, and seconds.
At least 15 minutes was needed to calculate the planetary position with the use of a table for each celestial body. [9] A horoscope of that era would have required the positions of seven astronomical objects, requiring nearly two hours of manual calculation time.
The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.
The program can calculate solar declination, Equation of Time, or Analemma; Doing calculations using Ptolemy's geocentric planetary models with a discussion of his E.T. graph; Equation of Time Longcase Clock by John Topping C.1720; The equation of time correction-table A page describing how to correct a clock to a sundial
These tables were used to calculate the world's ephemerides between 1900 and 1983, so this second became known as the ephemeris second. In 1967 the SI second was made equal to the ephemeris second. [34] The apparent solar time is a measure of Earth's rotation and the difference between it and the mean solar time is known as the equation of time.
The horizontal, or altitude-azimuth, system is based on the position of the observer on Earth, which revolves around its own axis once per sidereal day (23 hours, 56 minutes and 4.091 seconds) in relation to the star background. The positioning of a celestial object by the horizontal system varies with time, but is a useful coordinate system ...