Key to Geocentric Ephemeris of the Planets



An ephemeris is a table of values that gives the positions of astronomical objects in the sky over a range of times, while geocentric means "as seen from Earth's center." The following table is a key to the geocentric ephemeris of the planets and includes a description of each column in these tables.

Key to Geocentric Ephemeris of the Planets
Column Heading Definition/Description
1 Date
(0 UT)
Calendar Date (Gregorian).
All ephemeris positions are for 00:00:00 UTC
(Coordinated Universal Time).
2 Apparent
R.A.
Apparent Right Ascension of the planet for the true equator
and equinox of date (hours, minutes, seconds).
3 Apparent
Declination
Apparent Declination of the planet for the true equator
and equinox of date (degrees, arc-minutes, arc-seconds).
4 Distance
to Earth
Distance of the planet from Earth in astronomical units
(1 a.u. = 149,597,871 km).
5 Distance
to Sun
Distance of the planet from the Sun in astronomical units
(1 a.u. = 149,597,871 km).
6 App.
Mag.
Apparent Visual Magnitude of the planet.
7 Ang.
Diam.
Apparent Angular Diameter of the planet (arc-seconds).
8 Phase
Illum.
Phase Illumination
Fractional area (or diameter) of the planet's apparent disk illuminated by sunlight.
9 Phase
Angle
Phase Angle is the Sun-planet-Earth angle.
It is the angle between the Sun and Earth as seen from the planet (degrees).
10 S.E.
Long.
Sub-Earth Longitude of the central point of the planet's disk (degrees).
11 S.E.
Lat.
Sub-Earth Latitude of the central point of the planet's disk (degrees).
12 P.A.
Axis
Position Angle of the planet's rotation axis, measured eastwards (counter-clockwise) in the sky from the celestial north point of the planetary disk (degrees).
13 Ls Planetocentric Orbital Longitude of the Sun, measured eastward in the planet's orbital plane from planet's vernal equinox (degrees). Values of 0°, 90°, 180°, and 270° correspond to the beginning of spring, summer, autumn, and winter, in the planet's northern hemisphere.
14 Solar
Elong.
Solar Elongation of the planet.
Defined as geocentric angular position of the planet with respect to the Sun (degrees).
'E' is east (evening sky) and 'W' is west (morning sky).