The September 27, 2015, Lunar Eclipse
What is a lunar eclipse?
On the evening of Sunday, September 27, 2015, Acadiana sky watchers will have a chance to see the best total
lunar eclipse visible here in years!
Lunar eclipses happen when the moon
goes through Earth’s shadow. This
typically happens a couple times every
year somewhere in the world, and can
only happen at full moon. Because the
moon itself passes through Earth’s
shadow, the eclipse can be seen over
nearly half the earth—anywhere the
moon is visible during the event. By
contrast, solar eclipses—when the
moon passes directly between Earth
and the sun—can only be seen where
the moon’s shadow touches the earth.
Lunar eclipses don’t happen every
month because the moon’s orbit is tilted compared to the plane of the ecliptic (the approximate plane of our
planetary system and the region where Earth’s shadow must always fall). In most months the full moon appears
a little above or below Earth’s shadow so that no eclipse occurs. A lunar eclipse requires a fairly precise
alignment of the sun, Earth, and moon.
There are three kinds of lunar eclipses: penumbral, partial, and total. A penumbral
eclipse happens when the moon passes only through the outer shadow, or
penumbra, of Earth. A partial eclipse happens when the moon passes partially
through the dark inner shadow, or umbra, of Earth. Total eclipses begin
penumbral and go through a time of partial eclipse, but then completely enter
Earth’s umbra during totality; as the moon continues to move around Earth,
totality ends and is followed by another partial phase and by another penumbral
phase. The whole event lasts several hours.
433 Jefferson Street, Lafayette, LA 70501, 337-291-5547
It may seem odd that Earth could have both an inner and outer shadow, but that happens because the sun is
bigger than Earth. Sunlight from one side of the sun creates a shadow behind Earth that lies in a slightly
different direction from the shadow caused by light from the other side of the sun. The inner, umbral shadow is
that region that is completely shadowed from the sun while the outer, penumbral shadow is the region that is
shadowed from some (but not all) of the sun.
During a total lunar eclipse the moon turns color and may appear anywhere from a very dark red to a brighter
coppery-orange. This is caused by the scattering of sunlight passing through Earth’s atmosphere, with the
reddish colors then being bent onto the moon. It’s hard to predict the color of any particular eclipse because it
depends on Earth’s worldwide atmospheric conditions at the moment of the eclipse!
The Internet can make anything seem wacky
Over the last several years the phrase “blood moon” has been invented for lunar eclipses, a crackpot phrase
apparently designed to make the moon passing through Earth’s shadow seem somehow more dangerous than,
say, you walking through the shadow of a building. It’s a good phrase to ignore unless you want other people to
think you’re the crackpot. Grown-ups call these events “total lunar eclipses.” And if your blood actually is the
color of a lunar eclipse, you might want to see your doctor!
How to see this lunar eclipse
Lunar eclipses can be seen with just the unaided eye. No other equipment is needed, and the eclipse is
completely safe to watch (it’s a solar eclipse that will damage your vision). That being true, binoculars give a
beautiful view of a total lunar eclipse and a telescope can help you see the edge of Earth’s umbra as it covers
individual craters.
Happening in “prime time,” this will be the most conveniently timed total lunar eclipse for Acadiana since
2008, and there won’t be one to match it until 2022. The essentially unnoticeable penumbral eclipse will begin
at 7:12 p.m. CDT (minutes after moonrise in the east), but there won’t be much to see until the partial phase
starts at 8:07. The moon will move into Earth’s shadow as the moon rises into the southeast. Totality starts at
9:11 p.m. and lasts until 10:23, with mid-eclipse at 9:47. The final partial phase will end at 11:27 p.m. and the
virtually unnoticeable penumbral phase will end at 12:22 a.m. Monday morning.
You may read or hear that the eclipse will happen on September 28 rather than the 27th, but that’s just because
of the change in time zone from “Universal Time” (the standard in astronomy) to Central Daylight Time. Don’t
be confused—in Louisiana’s time zone, the eclipse is the night of the 27th!
Weather permitting, the Lafayette Science Museum and Planetarium will have telescopes in Parc Sans Souci in
downtown Lafayette for free public viewing of the eclipse. Although Acadiana observers will be able to see the
eclipse from wherever they live, why not join us for the fun?
433 Jefferson Street, Lafayette, LA 70501, 337-291-5547