How to see the eclipse of the moon Wednesday morning

The first visible total eclipse of the moon since 2015 occurs Wednesday in the predawn sky.

Portions of the eclipse will be visible across North America. However, the West Coast — especially Washington and Oregon — is ideally suited for watching all phases of the eclipse.

Keep your fingers crossed for clear skies — forecasts don’t sound very sunny. The next total eclipse visible across the Northwest takes place in 2019.

A total lunar eclipse takes place when the moon passes through the dark center, known as the umbra, of the Earth’s shadow. This only happens during a full moon and when the sun, moon and Earth are aligned like three birds sitting on a wire.

A lunar eclipse doesn’t happen during every full moon because the moon’s orbit around the Earth normally passes above or below our planet’s shadow.

This week, the moon will be 222,000 miles from Earth. At that distance, Earth’s cone-shaped shadow is 5,600 miles wide (2.5 times wider than the moon) and nearly 1 million miles long.

On Tuesday, the full moon rises in the northeast sky at about 4:18 p.m.

For the next 12 hours, two things prepare the moon for passing directly through Earth’s shadow.

First, the Earth’s eastward rotation moves the moon westward in the sky — from moon rise to moon set. This motion is easily noticed, especially when you’re watching the moon pass behind the limbs of a tree or across a neighbor’s house.

Second, a discerning observer will notice that relative to background stars, the moon is also slowly edging eastward due to its orbit around the Earth.

The first hint of Wednesday’s eclipse begins at 3:48 a.m. as the Earth’s curved shadow begins to darken the left edge of the full moon. With each passing minute, the moon buries itself deeper inside the shadow until becoming totally immersed at 4:51 a.m.

This marks the beginning of more than one hour of totality — the most colorful phase of the eclipse.

The copper and orange hues of the eclipsed moon originate from sunlight filtering through the thin rind of sunrises and sunsets encircling the Earth.

During totality, no direct sunlight falls upon the moon’s surface because the Earth acts like a cosmic umbrella blocking the sunlight.

The eclipse’s color depends upon the amount of cloudiness and dust in the Earth’s atmosphere. The clearer the atmosphere, the brighter the eclipse. The more opaque the atmosphere, the darker the eclipse.

In 1982, I watched a total lunar eclipse from atop Rattlesnake Mountain. Rather than seeing the eclipsed moon just turn orange, to my surprise, large dark blotches moved slowly across a deeply red tinted lunar landscape. At times, the moon even disappeared into the darkness of night. This darkness was caused by dust ejected into the Earth’s atmosphere earlier that year from an eruption of the El Chichon volcano in Mexico.

Totality ends at 6:08 a.m. when the moon’s left side starts brightening and departing from the umbra. Slowly the moon once again glows a familiar charcoal gray. Soon dawn brightens the sky.

The moon’s final partial eclipse phase ends at 7:12 a.m. Now the full moon is just a few minutes from setting in the northwest.

The best way to view the eclipse is with your unaided eyes, though binoculars can be helpful. Dress warm if you step outside. Otherwise, set the alarm clock and watch the eclipse from a west facing window inside your house.

By the way, on average it takes 2 to 3 years for a total eclipsed moon to be visible from the same location. By comparison, nearly 375 years pass between total solar eclipses observed from the same locale.

This story was originally published January 27, 2018 at 5:26 PM with the headline "How to see the eclipse of the moon Wednesday morning."