Viewer's Guide: Total Lunar Eclipse Saturday Evening

A total lunar eclipse this Saturday will last 74 minutes for viewers favorably positioned in Europe, Africa, or the eastern half of North America. For many, however, this could be a tricky eclipse to observe.

In the Western United States, the Moon won't rise until the event is largely over.

Meanwhile, many skywatchers in central and eastern parts of the United States and Canada should make special preparations to view this eclipse, since the event will be underway as the Moon rises in many locations.

• Full Eclipse Guide
• Top 10 Eclipse Facts

Trick of light

For North Americans, the farther East you go the better the view; as the Sun sets in the West, the Moon will coming up on the opposite side of the sky in the East.

Here's a neat trick: Try to see the partially eclipsed rising Moon and the setting Sun simultaneously.

Such an alignment during an eclipse might seem impossible. But thanks to Earth's atmosphere, the images of both Sun and Moon are apparently "lifted" above the horizon by atmospheric refraction of the light coming from them.  This allows us to see the Sun for several extra minutes after it actually has set and the Moon for several extra minutes before it actually rises.

From Newfoundland, the start of the partial stages begins very soon after moonrise.  From Nova Scotia, Prince Edward Island and New Brunswick, about one-quarter to one-half of the rising Moon will already be immersed in Earth's shadow, called the umbra. The shadow will creep almost straight up across the Moon's face from its lower limb. 

Across southeastern Quebec, New England and eastern New York, only the uppermost portion of the Moon will be in view as it comes above the eastern horizon.  Farther to the west and south, the Moon will rise completely immersed in the Earth's shadow. 

The timing

The table below shows the circumstances during the eclipse for select locations. Moonrise Magnitude is the fraction of the Moon's diameter within the Earth's full, umbral shadow at moonrise.  For example: from Boston, when the Moon rises at 5:30 p.m., 83-percent of the Moon's diameter will be inside the umbra.

Depending on the clarity of your sky, however, you might have to wait perhaps up to 15 minutes after sunset for the sky to darken enough, and the Moon to rise 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. 

The Moon will rise in total eclipse across a nearly 1,000-mile (1,600-kilometer) swath that will encompass the Middle Atlantic, Southeast and Deep South, western and central New York, the Ohio Valley, the Great Lakes and easternmost sections of the Central Great Plains.

Indeed, if the Moon is totally eclipsed at moonrise from where you live, you'll probably have to carefully scan the eastern horizon initially with binoculars as the twilight deepens in order to detect the Moon, somewhat resembling a dim, sooty and eerily illuminated mottled softball.

Waiting, waiting ...

I can vividly recall the total lunar eclipse of November 18, 1975, which I observed from the parking lot of the Hall of Science in Flushing, Queens. 

It was a balmy Indian summer evening and there was a bit of haze as the Sun set in the southwest and the Moon rose in the northeast.  At that time, about two-thirds of the Moon was already eclipsed, so I (and the hundreds of others who gathered to watch the eclipse) were hoping to see it emerge from beyond the horizon.  But we couldn't because there was a thick layer of haze and industrial smoke (what I like to call "atmospheric schmutz") that precluded seeing any vestige of the Moon until it cleared that haze layer nearly 45 minutes later. 

By then, totality had already begun, but from that moment on, the rest of the eclipse was clearly visible.

Farther West

For the central portions of the United States and Canada, the Moon's emergence from the umbra somewhat later will be the main spectacle.

The low, partially eclipsed Moon in deep blue twilight should offer a wide variety of interesting scenic possibilities for both artists and astrophotographers.  Over the Midwest, south to the Gulf Coast, a peculiar looking waning crescent Moon will appear to rise above the eastern horizon.  Farther west, across the Great Plains, the Moon will appear to be notched on its upper right side by the shadow. 

Going still farther west, the Moon will come up "full" but observers in Montana, Wyoming, Colorado, New Mexico and westernmost Texas might still be able to detect a penumbral stain on the Moon's upper right limb if the eastern horizon is haze-free.  It might look like the famous "Man-in-the-Moon" has a bruise over his left eye.  I'd be interested in hearing from those out west who detect the penumbra on the rising Moon.  When you E-mail me, be sure to indicate your location and any instrument you might have used.

Unfortunately, the West Coast misses out completely, but observers there can be consoled by the knowledge that they will get their chance at another total lunar eclipse on Aug 27.

More about the Moon

• Top 10 Luna-Terms
• Top 10 Eclipse Facts
• Top 10 Cool Moon Facts
• Skywatcher's Guide to the Moon
• Why Does the Moon Look Bigger on the Horizon?
• More Lunar News, Facts and Lore

Basic Sky Guides

• Astrophotography 101
• Sky Calendar & Moon Phases
• 10 Steps to Rewarding Stargazing
• More Skywatching News & Features

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.