How to Watch the ‘Blood Moon’ Total Lunar Eclipse

From Thursday night into Friday morning, Earth’s shadow will swallow the moon, transforming the usually pearly orb into a striking red sphere.

It’s the first total lunar eclipse in more than two years. Also known as a blood moon, the event will be most visible across the Americas, western parts of Africa and Europe, New Zealand and some of Russia.

“It’s a lovely sight to see in the night sky,” said Amanda Bosh, the executive director of the Lowell Observatory in Arizona, who has seen more than 20 lunar eclipses in her lifetime.

“I love seeing the solar system, the universe, at work,” she added.

What is a total lunar eclipse?

A lunar eclipse occurs when the sun, Earth and moon align, in that order. There are different types of lunar eclipses that depend on how deeply the moon crosses into Earth’s shadow, which is divided into an outer part, the penumbra and the umbra, the innermost section.

A total lunar eclipse, when the entire moon slips into the umbra, is by far the most dramatic variety. Earth’s shadow envelops the face of the moon, causing it to shine scarlet. This happens because sunlight spilling over the edges of Earth and lighting up the lunar surface must first travel through our atmosphere, which more readily scatters blue wavelengths of light. Redder wavelengths pass through, creating the blood-moon effect.

According to Dr. Bosh, the exact shade of red during a lunar eclipse can vary. Clouds and recent natural disasters — like dust storms or volcanic eruptions, which leave particles in the air — can make the moon appear more crimson.