Total Lunar Eclipse On Wednesday Will Be a Rare 'Selenelion'
By Joe Rao, Space.com Skywatching Columnist | October 06, 2014 01:35pm ET
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A photo of the first total lunar
eclipse of 2014 taken from
Arizona.
Credit: Ron Delvaux via The Virtual
Telescope Project
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Observers of Wednesday morning's total lunar eclipse might be able to catch sight of an extremely rare cosmic sight.
On Oct. 8, Interested skywatchers should attempt to see the total eclipse of the moon and the rising sun simultaneously. The little-used name for this effect is called a "selenelion," a phenomenon that celestial geometry says cannot happen.
And indeed, during a lunar eclipse, the sun and moon are exactly 180 degrees apart in the sky. In a perfect alignment like this (called a "syzygy"), such an observation would seem impossible. But thanks to Earth's atmosphere, the images of both the sun and moon are apparently lifted above the horizon by atmospheric refraction. This allows people on Earth to see the sun for several extra minutes before it actually has risen and the moon for several extra minutes after it has actually set. [How to See the Total Lunar Eclipse (Visibility Maps)]
As a consequence of this atmospheric trick, for many localities east of the Mississippi River, watchers will have a chance to observe this unusual sight firsthand. Weather permitting, you could have a short window of roughly 2 to 9 minutes (depending on your location) with the possibility of simultaneously seeing the sun rising in the east while the eclipsed full moon is setting in the west.
Regions of visibility
From Newfoundland, the start of the partial stages of the total eclipse begins about 30 to 45 minutes before moonset.
A growing scallop of darkness will appear on the upper left part of the moon when it sets as the sun is coming up. Across eastern Nova Scotia, only the lowermost portion of the moon will be in view as it drops below the western horizon. Farther to the west and south along the Atlantic seaboard, the moon will rise completely immersed in the Earth's shadow.
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The map shows the visibility regions for the Oct. 8, 2014 total lunar
eclipse, which is
the second of four consecutive total eclipses of the
moon between 2014 and 2015.
Sky & Telescope Magazine released this
viewing map.
Credit: Sky & Telescope Magazine
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Now you see it … now you don't?
Then again, sighting a selenelion might be problematic feat.
Twenty-five years ago, in the August 1989 issue of Sky & Telescope,
Bradley Schaefer, an astronomer who extensively studied the visibility
of the moon when it was low in the sky, noted that the full moon only
becomes visible when it is about 2 degrees up and the sun is about 2
degrees below the horizon.
So, depending on the clarity of your sky, you might have up to roughly
10 to 15 minutes before sunrise for the sky to still be dark enough, and
the moon to be high enough above any horizon haze for it to be clearly
visible. And keep in mind that this holds only for the uneclipsed
portion of the moon. You might, however, be able to mitigate the effects of a brightening sky somewhat by using binoculars or a telescope.
If the moon is totally eclipsed prior
to sunrise, you probably are going to have to scan the western horizon
with binoculars as the twilight brightens in order to still detect some
semblance of the Moon, which will somewhat resemble a very dim and
eerily illuminated mottled softball.
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This chart shows the times of the end-stages of a total lunar eclipse taking place on
Oct. 8, 2014.
Credit: Space.com/Joe Rao
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A peculiar moonset
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A series of four total
lunar eclipses in a row
is called a tetrad. See
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People who live in those portions of the United States and Canada that
are a few hundred miles inland from the Eastern Seaboard should have a
good view of the Moon's emergence from the umbra somewhat later. The
low, partially eclipsed Moon in deep-blue twilight should offer a wide
variety of interesting scenic possibilities for both artists and
astrophotographers. From Toronto and points south through the eastern
Ohio Valley and into the Piedmont to the Florida Gulf Coast, a
peculiar-looking, waxing crescent moon with its cusps pointing downward
will appear to set beyond the western horizon.
Farther west, across the western Great Lakes and down through the Deep
South to the Gulf of Mexico, the moon will appear to be notched on its
lower right side by the shadow.
Going still farther west, the Moon will go down "full," but if the
western horizon is haze-free, assiduous observers from much of
Minnesota, western Iowa, eastern portions of Nebraska and Kansas as well
as central sections of Oklahoma and Texas might still be able to detect
a faint penumbral stain on the moon's lower right limb.
Editor's Note: If you snap an amazing picture of the
Oct. 8 total lunar eclipse, you can send photos, comments and your name
and location to managing editor Tariq Malik at spacephotos@space.com.
Joe Rao serves as an instructor and guest lecturer at New York's
Hayden Planetarium. He writes about astronomy for Natural History
magazine, the Farmer's Almanac and other publications, and he is also an
on-camera meteorologist for News 12 Westchester, N.Y. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.
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Author Bio
Joe Rao
Joe Rao is a television meteorologist in the Hudson Valley, appearing weeknights on News 12 Westchester. He has also been an assiduous amateur astronomer for over 45 years, with a particular interest in comets, meteor showers and eclipses. He has co-led two eclipse expeditions and has served as on-board meteorologist for three eclipse cruises. He is also a contributing editor for Sky & Telescope and writes a monthly astronomy column for Natural History magazine as well as supplying astronomical data to the Farmers' Almanac. Since 1986 he has served as an Associate and Guest Lecturer at New York's Hayden Planetarium. In 2009, the Northeast Region of the Astronomical League bestowed upon him the prestigious Walter Scott Houston Award for more than four decades of promoting astronomy to the general public.
Joe Rao on 
