Explanation of Lunar Eclipse Data Tables
by Fred Espenak
The following tables contain brief explanations for the various parameters used in the prediction of lunar eclipses.
Eclipse Characteristics 
Parameter 
Description 
Penumbral Eclipse Magnitude  the fraction of the Moon’s diameter occulted by Earth’s penumbral shadow at the instant of Greatest Eclipse;
the Penumbral Eclipse Magnitude is less that 1.0 for partial penumbral eclipses (and equal to or greater than 1.0 for total penumbral eclipses); the Penumbral Eclipse Magnitude is equal to or greater than 1.0 for most partial eclipses and for all total eclipses 
Umbral Eclipse Magnitude  the fraction of the Moon’s diameter occulted by Earth’s umbral shadow at the instant of Greatest Eclipse;
the Umbral Eclipse Magnitude is less that 1.0 for partial eclipses (and less than 0.0 for penumbral eclipses); the Umbral Eclipse Magnitude is equal to or greater than 1.0 for total eclipses 
Gamma  the distance (in units of equatorial Earth radii) of the center of the Moon’s disk from the center of Earth’s umbral shadow at the instant of Greatest Eclipse; since this is the instant when the Moon passes closest to the axis of Earth’s umbral shadow, Gamma is, by definition, the minimum distance of the shadow axis from center of the Moon

Epsilon  the apparent geocentric angular distance (in degrees) of the center of the Moon’s disk from the center of Earth’s umbral shadow at the instant of Greatest Eclipse; Epsilon is, by definition, the minimum angular distance of the Moon from the shadow axis during a lunar eclipse

Conjunction Times 
Parameter 
Description 
Greatest Eclipse  the instant when the Moon’s disk passes closest to the center of Earth’s shadow
(by convention the date of an eclipse is fixed to this instant) 
Ecliptic Opposition  the instant when the Sun and Moon have ecliptic longitudes differing by 180° this defines the instant of the Full Moon phase 
Equatorial Opposition  the instant when the Sun and Moon have celestial longitudes differing by 180° in the equatorial coordinate system; this is the instant when the Sun and Moon Right Ascensions differing by 12 hours 
Geocentric Coordinates of Sun and Moon 
Parameter 
Description 
Right Ascension  the longitudinal position (in the equatorial coordinate system) of the Sun and the Moon at the instant of greatest eclipse 
Declination  the latitudinal position (in the equatorial coordinate system) of the Sun and the Moon at the instant of greatest eclipse 
SemiDiameter  the apparent geocentric angular radius of the disk of the Sun or Moon at the instant of greatest eclipse 
Eq. Hor. Parallax  Equatorial Horizontal Parallax, the angle subtended by the radius of Earth at the distance of the Sun or Moon at the instant of greatest eclipse 
Geocentric Libration of Moon 
Parameter 
Description 
l  the Moon’s geocentric libration in longitude at greatest eclipse 
b  the Moon’s geocentric libration in latitude at greatest eclipse 
c  the Moon’s geocentric libration in position angle of lunar rotation axis with respect to celestial north 
Earth’s Shadows 
Parameter 
Value 
Penumbral Radius  the apparent geocentric angular radius (in degrees) of Earth’s penumbral shadow at the distance of the Moon at the instant of Greatest Eclipse 
Umbral Radius  the apparent geocentric angular radius (in degrees) of Earth’s penumbral shadow at the distance of the Moon at the instant of Greatest Eclipse 
Prediction Parameters 
Parameter 
Description 
Ephemerides  identifies the ephemerides used to calculate the postions of the Moon and Sun 
ΔT  the value of ΔT used in the eclipse predictions 
Shadow Rule  the computational method used for enlarging Earth's radius to compensate for the effects of the atmosphere on eclipse contact times; see Earth’s Shadow for more information 
Shadow Enlargement  the fractional enlargement of Earth's penumbral and umbral shadows used in the eclipse predictions; see Earth’s Shadow for more information 
Saros Series  the Saros series number followed by the sequence number and total number of eclipses in the series 