The following article is taken from Astronomy Magazine.
We’ll experience the first total lunar eclipse in 28 months the morning of Tuesday, April 15. Observers throughout North and South America will have the prime views of this eclipse. Those in the western Pacific will miss the first half of the eclipse because it occurs before the Moon rises. Likewise, most of Europe and Africa will experience moonset just as the eclipse begins.
A lunar eclipse occurs when the Sun, Earth, and the Moon line up. During such times, the Moon passes through Earth’s shadow, and where it passes determines the type of eclipse we’ll see. Our planet’s shadow has two parts: a darker inner section called the umbra and a lighter outer region called the penumbra. When the Moon passes through only the penumbra, we experience a penumbral eclipse. When only some of it passes through the umbra, we see a partial eclipse. Sometimes, however, all of the Moon passes through the umbra, creating a total lunar eclipse. That’s what’s happening on the 15th.
For more than an hour you’ll see the dark part grow until totality begins at 3:07 a.m. EDT. Totality lasts 78 minutes, until 4:25 a.m. EDT. The partial phase is over at 5:33 a.m. EDT, and the penumbral phase —and this eclipse — ends at 6:38 a.m. EDT.
The Moon’s appearance during totality can vary greatly from one eclipse to the next. The path the Moon takes through Earth’s umbra — and how centered it is — has an effect. But so does our atmosphere. It can darken the shadow because it contains water droplets and solid particles like dust and ash, which reduce the air’s clarity. Lots of clouds along the edge of our planet also can cut down the light.
But in addition to appearing dark, the Moon takes on a particular color during totality. This occurs because our air bends some of the Sun’s rays into the shadow. It also scatters the shorter (bluer) wavelengths out of that light, reddening it and darkening the Moon’s face.Next Tuesday morning, the Moon’s northern edge passes a tiny bit south of the shadow’s center. In contrast, its southern edge lies a lot farther from that point. As a result, the Moon’s northern half will look much darker than its southern half because it lies deeper in the umbra.
During totality, the constellations of the Northern Hemisphere’s spring surround the Moon. Mars will dazzle 9.4° northwest of the Moon. On eclipse morning, the Red Planet lies relatively close to Earth and shines at magnitude –1.4, as brightly as it will until 2016. It’s also as large as it will be until then, so if you have a telescope set up for the eclipse, you’ll have plenty of time to steal a glance at Mars, even during totality.
Astronomy Senior Editor and veteran eclipse watcher Richard Talcott notes how safe this event is to watch. “A lunar eclipse poses no danger whatsoever to your eyes,” he says. “All you’re looking at is the Moon passing through a big shadow. Not only do you not need any filters, but you also can feel free to magnify the sight by using binoculars or a telescope.”
Paul
