Ephemeris (from the Greek: εφημερος ( Ephemeros ) = " for a day " from επι (epi ) = "on " and " ημέρα ( Hemera ) =" day " ) are carved work or tables showing the positions of moving astronomical objects in constant intervals included. In a narrower sense it is (daily ) tables position of the sun, moon, planets, comets, and fixed stars.
Ephemeris are used in addition to astronomy in celestial mechanics, geodesy and astro in the space. Other applications related to solar, planetary or earth satellites and astrology are using such tables.
In printed form ephemeris are as Astronomical yearbooks or for the seafaring nautical yearbooks. Among the earliest astronomical printing include the 1474 published Ephemerides of Regiomontanus astronomicae that used Christopher Columbus on his voyages of discovery to the navigation.
Ephemeris for observational astronomy use of for position indication either of the full circle of 360 degrees along the ecliptic, or enter the position in equatorial coordinates. The calculation of the ephemeris is one of the achievements of the astronomical phenomenology and is now part of many astronomical programs or interactively on the Internet.
In a satellite ephemerides describe in mathematical terms the apparent orbit. The Global Positioning System (GPS) and other GNSS systems, this data path are part of the emitted signal from each satellite, which are then the basis for the calculation of the receiver position.
To estimate the probability of a collision of two bodies in the solar system, it is necessary to know the exact positions of the body and the temporal evolution of their orbital elements. Therefore ephemeris catalogs are created for asteroids to determine their most inadequately known web data precisely. Particular attention is given to the Earth's orbit cruisers, their impacts on the earth could be a threat.
Astrological Ephemeris enter the ecliptic longitude of the stellar positions as degrees of the zodiac. The specification of the ecliptic latitude is not common in all astrological ephemeris.
Of special importance is the calculation of the actual aspects of construction and destruction, and the Tagbogens the sun for calculating the effectiveness of solar systems as well as in the architecture for an estimate of the solar incidence; this is implemented in CAD software usually as a light module.
The ephemeris as a field of activity of the astronomical phenomenology is made on the basis of actually observed positions of celestial bodies and the theory of gravitation. While the expected perturbations are taken into account for future values . To this end, computational models are set up as the planetary theory, to specify the perturbation theory. The free software module Swiss Ephemeris is used in a variety of application programs for the calculation of planetary and star positions.
Important historical panel works for the ephemerides were the Alfonsine Tables, the Prutenischen boards and Rudolf's panels.
Time reference and table intervals
The panel intervals of the tabulated coordinates depends on their rate of change or the web speed. In fundamental stars and distant planet 10 days customary in the sun, moon and inner planets 1-2 days.
The arguments ( time points) of the tabulated coordinates can refer to different time systems:
In [2, 3] also times in fractions of a day are common rather than hours.