Download Skyward April 2016 A Penumbral eclipse of the Moon I have now

Skyward
April 2016
A Penumbral eclipse of the Moon
I have now seen 83 eclipses during my life, ranging from total eclipses of the Sun (I’ve
seen 11 of those) to, at the other extreme, penumbral eclipses of the Moon. And of all the different
kinds of eclipses I have witnessed, these soft, gentle events in which the Earth’s shadow gently
kisses the Moon are probably my favorite, because they are so difficult to detect. My most recent
eclipse was one of these, a penumbral lunar eclipse that took place in the predawn hours of March
23, 2016.
Eclipses are a cosmic coincidence. When the Moon passes through the Earth’s partial
shadow, a penumbral eclipse occurs. If it passes through a portion of the Earth’s full or umbral
shadow, there is a partial or total lunar eclipse. When the Moon passes in front of the Sun, it casts
its own shadow on a portion of the Earth, and we can see a solar eclipse.
Even though almost 8/10 of the Moon was covered by the shadow of the earth, or at least
some of the shadow of the earth, this eclipse was almost impossible to detect. Without using a
telescope, my friend Tim Hunter was unable to detect any shading at all. When I stepped out at
3:30 AM, more than an hour before the middle of the eclipse, the full moon looked like any other
full moon; an hour later the moon looked exactly the same. But then I viewed the Moon through
Pegasus, the 8 inch-diameter reflector telescope I have used since 1964. This telescope gave a
slightly different interpretation to what I was seeing; instead of the clean lunar surface with which
I was familiar, the entire southern hemisphere of the Moon looked slightly brownish. The view
was ethereal, gorgeous quite beyond description, and a wonder to behold. The photographs I took
of that eclipse revealed no such darkening, at least not to the extent I could detect within the
camera’s viewfinder. But visually, a definite slight shading was there.
The March 23 eclipse took place on our 19th wedding anniversary; in fact as a date March
23 is one of the most interesting days of my year. On March 23, 1963, while a patient at the
Jewish National Home for Asthmatic Children in Denver, I mapped the winter regions of the
Milky Way with my small telescope. On March 23, 1990, I recorded my first observation of an
explosion of Tombaugh’s star, the variable star Clyde Tombaugh discovered on photographic
plates he had taken on March 23, 1931, exactly 59 years earlier. Most important for me, on March
23, 1993, using a telescope on Palomar Mountain in California, I exposed two wide-angle
photographic films of a region of the sky containing the planet Jupiter. Two days later Carolyn
Shoemaker discovered a comet on those images. Subsequently named Shoemaker-Levy 9, this
particular comet, whizzing through space at 140,000 miles per hour, collided with Jupiter in 1994,
giving humanity’s first vision of an encounter between two large solar system objects. Perhaps it
was another cosmic coincidence that Wendee and I chose that date to get married in 1997.
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In 2006 I observed a very rare “total Penumbral” lunar eclipse during which the Moon
grazed the edge of the Earth’s central shadow without actually involving itself in any of it.
Although this eclipse was not visible from our Arizona home, it could be seen several hundred
miles to the east. Accordingly I made certain that I was on an American Airlines plane traveling
from Tucson to Chicago at the time of the eclipse. This time the shading was obvious, although it
was still a challenge to see. That eclipse took place in the early evening of March 14, 2006; just
two weeks later Wendee and I saw a second eclipse, this time a total eclipse of the Sun visible from
the Aegean Sea off the eastern coast of Greece. I can write without hesitation that I do not know of
a sight more awe-inspiring, more wonderful, more exciting, and more emotionally satisfying than
the total phase of an eclipse of the Sun. Last month’s penumbral eclipse of the moon cannot
compare to a total solar eclipse, but like its more famous kindred, such an eclipse also shows that
the night sky is not static; the Sun, the Moon, and the planets appear to move in front of the more
distant panorama of stars. Sometimes Mercury or (much less often) Venus will transit, or cross the
face of, the Sun. Next month, on May 9, Mercury will transit the Sun. You’ll need a telescope
and a proper filter to see it. Eclipses and transits are the result of the regular movements of the
Sun and the Moon, and they prove that the sky is a place where wonderful things can happen.