The limits of the Moon's penumbral shadow define the region of visibility of
the partial eclipse. This saddle shaped region often covers more than half of
Earth's daylight hemisphere and consists of several distinct zones or limits.
At the northern and/or southern boundaries lie the limits of the penumbra's
path. Partial eclipses have only one of these limits, as do central eclipses
when the shadow axis falls no closer than about 0.45 radii from Earth's center.
Great loops at the western and eastern extremes of the penumbra's path identify
the areas where the eclipse begins/ends at sunrise and sunset, respectively.
If the penumbra has both a northern and southern limit, the rising and setting
curves form two separate, closed loops. Otherwise, the curves are connected in
a distorted figure eight. Bisecting the 'eclipse begins/ends at sunrise and
sunset' loops is the curve of maximum eclipse at sunrise (western loop) and
sunset (eastern loop). The exterior tangency points **P1** and **P4**
mark the coordinates where the penumbral shadow first contacts (partial eclipse
begins) and last contacts (partial eclipse ends) Earth's surface. If the
penumbral path has both a northern and southern limit (as does the October 1995
eclipse), then the interior tangency points **P2** and **P3** are also
plotted and correspond to the coordinates where the penumbral cone becomes
internally tangent to Earth's disk. Likewise, the points **U1** and
**U2** mark the exterior and interior coordinates where the umbral shadow
initially contacts Earth (path of total eclipse begins). The points **U3**
and **U4** mark the interior and exterior points of final umbral contact
with Earth's surface (path of total eclipse ends).

A curve of maximum eclipse is the locus of all points where the eclipse is at maximum at a given time. They are plotted at each half hour Universal Time (UT), and generally run from northern to southern penumbral limits, or from the maximum eclipse at sunrise or sunset curves to one of the limits. The outline of the umbral shadow is plotted every ten minutes in UT. Curves of constant eclipse magnitude[5] delineate the locus of all points where the magnitude at maximum eclipse is constant. These curves run exclusively between the curves of maximum eclipse at sunrise and sunset. Furthermore, they are parallel to the northern/southern penumbral limits and the umbral paths of central eclipses. Northern and southern limits of the penumbra may be thought of as curves of constant magnitude of 0%, while adjacent curves are for magnitudes of 20%, 40%, 60% and 80%. The northern and southern limits of the path of total eclipse are curves of constant magnitude of 100%.

At the top of Figure 1, the Universal Time of geocentric conjunction between the Moon and Sun is given followed by the instant of greatest eclipse. The eclipse magnitude is given for greatest eclipse. For central eclipses (both total and annular), it is equivalent to the geocentric ratio of diameters of the Moon and Sun. Gamma is the minimum distance of the Moon's shadow axis from Earth's center in units of equatorial Earth radii. The shadow axis passes south of Earth's geocenter for negative values of Gamma. Finally, the Saros series number of the eclipse is given along with its relative sequence in the series.

[5] Eclipse magnitude is defined as the fraction of the Sun's diameter occulted by the Moon. It is usually expressed at greatest eclipse. Eclipse magnitude is strictly a ratio of

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