This weekend's blood moon will be hard to miss: The event will light up the sky for one hour and 43 minutes on July 27, making it the longest total lunar eclipse of the 21st century, according to Space.com.

A blood moon occurs when the Moon passes beneath Earth's shadow, giving it an eerie rust-colored appearance. Just how long the effect lasts depends on the the position of the Moon in relation to the Sun. For this upcoming lunar eclipse, the Moon will pass close to the center of Earth's umbra, or the darkest part of the planet's shadow, extending the duration of the eclipse. The Moon will also be at a point in its orbit where it's farther from us, which means it will spend even more time in Earth's shadow.

The time the Moon spends in the actual umbra will amount to one hour and 43 minutes. It will also spend considerable time in Earth's penumbra, which is the lighter part of its shadow. Including this portion, the eclipse will last 3 hours and 55 minutes in total.

Sky-gazers in North America are out of luck this time around: The blood moon will only be viewable from Africa, the Middle East, southern Asia, and the Indian Ocean region starting at 3:30 p.m. EDT and ending at 5:13 p.m. If you won't be in the right part of the world to catch this particular show, check out this space calendar to see what events are occurring over your neighborhood this summer.

[h/t Space.com]