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There was also something else at play, which made
it difficult to judge the overall intensity of the shadow’s
color. In Image 3, note how the southern highlands
(at the top) appear so much brighter than the remain-
der of the disk in shadow. This is not due to irregulari-
ties in Earth’s atmosphere, but rather due to albedo
effect. Lunar highlands ref lect twice as much light as
the darker maria, which dominate the shadowed
region.
This same phenomenon caused the first half of the
umbral eclipse to appear darker than the second half.
As Image 4 shows, the reason for the intensity differ-
ence is largely due to the greater amount of highland
material appearing in the deeper (redder) part of the
shadow during the second ha lf of the eclipse.
One other aspect of the eclipse surprised me. To my
naked eyes and through binoculars, the edge of the
Moon’s shadow appea red i r reg u la r (a cont r a st i l lu sion
created as the shadow covers the irregular boundariesof the maria), as you can see in Image 5 taken through
a 3-inch telescope at prime focus. Through the 8-inch,
however, the shadow’s edge remained smooth through-
out the eclipse, as it should.
Send your thoughts on any lunar eclipse to
[email protected].- The blue leading
edge of Earth’s
shadow is rimmed by
a smoky yellow deep
penumbral shadow. - As the eclipse
progressed, the edge
of Earth’s umbral
shadow appeared
irregular as it covered
the maria — to the
unaided eye and
through binoculars. - Two exposures of
the same length show
albedo differences in
Earth’s shadow. The
darker maria in the
exposure dominate
the view in the deep
shadow during
ingress (left). Highly
reflective highland
material dominates
the deep shadow
during egress (right).
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