A
lunar eclipse can be viewed from any place on
Earth's night side. During a total lunar eclipse, the
moon usually does not become completely dark, but
takes on a color similar to copper or blood. This is
because the moon's surface is still faintly lit by
the halo of Earth's sunrise / sunset skies, as some
sunlight is refracted around Earth by its atmosphere.
A lunar eclipse
begins with the
penumbral phase, in which the moon is dimmed by
Earth's outer shadow; such dimming is rather subtle,
and usually goes unnoticed by most people. The second
phase is the umbral, when the dark cone of
Earth's shadow contacts the moon and begins to
obscure larger and larger amounts of the moon's
surface. The third phase is totality, when the full
moon's entire surface is darkened by Earth's umbra.
Because Earth's shadow is large compared to the moon,
totality may last for a considerable time. Then, as
the moon begins to pass out of Earth's shadow, the
phases reverse.
The reason a lunar
eclipse does not occur at every full moon is that the
plane of the moon's orbit is tilted with respect to
the orbit of Earth around the sun. Because of this,
the full moon lines up with the sun and Earth only a
couple of times per year on average.
It is always safe to
view any lunar eclipse with the naked eye, or through
a camera lens, binoculars, or a telescope.
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