Watch the Total Lunar Eclipse (March 13-14)

It's been more than two years since observers in the Americas witnessed a total lunar eclipse. The wait ends Thursday night / Friday morning, March 13–14, when the full Moon slips back into Earth's shadow for 66 glorious and colorful minutes. All of totality and most of the partial phases will be visible throughout the Western Hemisphere. In the continental U.S., totality happens late at night, beginning at 11:26 p.m. for the West Coast and 2:26 a.m. for the East. While no optical aid is needed to observe the eclipse, be sure to set your alarm so you don't miss it!

Observers in western Europe and west Africa will see the Moon enter totality shortly before it sets around sunrise. On the other side of the planet, eclipse-gazers in Australia, New Zealand, and northeast Asia will see the Moon rise in partial eclipse as it exits Earth's shadow.

A lunar eclipse occurs only at full Moon, when Earth lies precisely between the Sun and the Moon, casting its shadow directly across our celestial neighbor's face. Since the Moon's orbit is tilted 5.1° with respect to the Sun-Earth plane, eclipses occur only when the Moon crosses that plane at the same time that it's full. This makes such events uncommon, with an average of two eclipses a year.

Cut off from sunlight, the eclipsed Moon would be invisible were it not for our atmosphere. The air acts like a lens and bends the solar rays that graze Earth's circumference into our planet's shadow cone. Only the reds and oranges make it into the umbra — the rest are scattered away by the air — the reason the Moon glows in warm colors during totality. Volcanic aerosols, cloud cover, and other factors cause the Moon's hue to vary at each eclipse from charcoal-brown to glowing magma to copper. Anticipating the color and brightness of the eclipsed Moon adds an element of surprise to every totality.

Although the Moon will dash along its orbit at some 3,550 kilometers per hour (2,200 mph) on eclipse night, from our perspective a quarter million miles away, it enters and exits the shadow slowly and inexorably. The show begins with a hint of penumbral shading along the Moon's (celestial) eastern edge and ends a little more than six hours later when the Moon slips out the other side.

Eclipse phases by time zone

What to expect During the Total Lunar Eclipse

Penumbral phase

• Approximately 30 to 40 minutes before the partial phase begins, look for penumbral shading covering the (celestial) eastern half of the Moon. Unlike the "bite" of the umbra, which is dark and distinct, the penumbral shadow is subtle and diffuse. If you have a DSLR or mirrorless camera, examine the Moon in live view mode at this time. During the last lunar eclipse, the shadow was obvious considerably earlier in my mirrorless camera compared to what I could see with my unaided eye.

Partial eclipse

• Through binoculars or a telescope, you'll notice that the transition from penumbra to umbra is fuzzy, not a hard boundary. This is because the Sun is an extended object rather than a point source. Light from a tiny fraction of the solar disk softens the darkness where inner shadow meets outer.
• When does the Moon's red-orange color first appear? Through a small telescope, it's noticeable within minutes after the start of partial eclipse. The unaided eye needs more time because of competition from lunar glare.

• The diameter of Earth's shadow varies slightly from eclipse to eclipse, beyond what basic geometry can explain. You can help measure its size by timing when the umbra's edge crosses the center of selected craters. Sky & Telescope Senior Contributing Editor Roger Sinnott has compiled a list of craters along with entry and exit times for the current eclipse. Please e-mail him your timings for later analysis.
• For complete instructions on crater-timing as well as additional eclipse activities, check out Roger's Useful Projects for a Lunar Eclipse.

Totality

• How dark and what color will the Moon be during totality? Both are affected by everything from the atmosphere's dust and aerosol content to cloud cover. Use the Danjon Scale (below) to estimate its brightness, and share your report with Sky & Telescope in the comments section.
• You can also estimate the Moon's overall magnitude at mid-totality using the "backwards" binoculars method (instructions here). Send your observations to Brazilian amateur astronomer Helio Carvalho at [email protected]. He'll use the data to model the state of Earth's atmosphere at the time.
• Carvalho predicts a bright eclipse. In an email communication, he noted that "Earth's stratosphere is currently clean of volcanic aerosols, since those injected by Tonga are already gone. Many other smaller eruptions have occurred since then, but most of them were tropospheric ones that had no significant impact on the stratosphere."

• Lucas Boissel, a PhD student in Geography at Université Paris Cité, is also interested in your Danjon estimates. He's studying the impact of volcanic eruptions on the atmosphere by analyzing historical observations of lunar eclipses. Boissel has provided this Google Doc to share and submit your observations.
• Once Earth's shadow snuffs out the Moon's glare, the stars return. Enjoy an hour of dark sky. To the east, the puffy star clouds of the summer Milky Way are on the rise, while in the west, the winter groups bid farewell. A lunar eclipse is a more languorous version of a total solar eclipse. Instead of a minutes-long transition from light to dark to light, you've oodles of time.
• Record video of the Moon through your telescope during totality to try to capture meteoroid impact flashes. Normally, these would be invisible against the bright, sunlit Moon, but the flashes stand out when the Moon is engulfed in shadow. Here are some tools that will be helpful in detecting impact signals in your recording.
• Take a few minutes to enjoy the umbral Moon framed by stars, an otherwise impossible sight during a non-eclipsed full Moon. Binoculars offer the best view.

After Totality

As the Moon begins to rebrighten, you can watch the show all over again but in reverse. One reason lunar eclipses are special is because they allow so much time for observation and photography.

Speaking of which, if you're photographing the Moon, it's best done with a telephoto lens or through a small telescope. If you don't own a digital camera, just hold your smartphone up to the telescope eyepiece to take pictures. Photos taken outside of totality require only a fraction of a second exposure. During total eclipse, you'll need to increase exposure times to several seconds. For an in-depth treatment of lunar eclipse photography, visit Rob Pettengill's Exposure Planning for a Lunar Eclipse.

Let's all hope for good weather. Even if there are clouds, though, we can still watch the show: Italian astronomer Gianluca Masi will livestream the eclipse at the Virtual Telescope Project starting at 11 p.m. CDT (04:00 UT) on March 13.

By happy coincidence, much of the eclipse occurs on Pi Day (March 14th), the annual celebration of the mathematical constant pi (π). Given 3.14159 . . .'s importance in astronomical calculations, the eclipse is a fitting paean.