Blood Moon coming up: the longest total eclipse of the century


Published: 2018-07-14 20:36

Last Updated: 2024-06-16 02:49

Total lunar eclipse of 2015 Pisa, Italy. (Giuseppe Petricca)
Total lunar eclipse of 2015 Pisa, Italy. (Giuseppe Petricca)

The longest lunar eclipse will occur on July 27th, 2018 and will last for one hour and 43 minutes. This astronomical event will continue for nearly four hours, during which the moon will turn into a spectacular ruddy-brown color.

The eclipse will be visible to viewers in the Middle East, Africa, southern Asia and the Indian Ocean region, according to lunar scientist Noah Petro, of NASA's Goddard Space Flight Center in Greenbelt, Maryland. The timing of the lunar eclipse means it won't be visible from North America.

According to, the total duration of the eclipse event will last from 10:30 p.m. until 12:14 a.m. local time, (19:30 to 21:13 GMT). The greatest eclipse will occur at 11:21 p.m. local time, (20:21 GMT).

The time before and after an eclipse is called the penumbra, when the moon is in the lighter part of Earth's shadow, making this coming event last a total of 3 hours and 55 minutes.

This NASA chart by eclipse expert Fred Espenak shows details and visibility projections for this “blood moon” eclipse.

Unlike solar eclipses, you don’t need special equipment to observe lunar ones. Lunar eclipses occur when the moon passes into Earth's shadow, and it is safe to view directly with the naked eye, telescopes and binoculars.

Instead of the moon going completely dark during an eclipse, it turns deep red or reddish brown because some of the passing sunlight through the Earth's atmosphere gets bent around the edge of the planet, and then reflects onto the moon's surface.

Moreover, Earth’s air scatters the shorter-wavelength light (like green or blue), making only the longer-wavelength visible (redder end of the spectrum).

This is the longest lunar eclipse of the century because the moon will be passing earth’s shadow, the umbra, right though the middle. “What controls the duration of the lunar eclipse is the position of the moon as it passes through the Earth's shadow,” Petro told

You can picture the umbra as a cone extending from Earth in the direction of the sun, Petro explained.

“The moon can either graze through the cone, or go right through the middle. [The middle] gets a longer-duration eclipse,” he said. “This time, the moon is passing closer to the center of that cone, and it's therefore a little bit longer than the eclipse we had back in January.”

However, as EarthSky pointed out, the moon will appear slightly smaller in the sky and will take a little bit longer to go through Earth's shadow as it will be at a farther point from the Earth along its orbit.