Curiosity and awe have greeted a complete lunar eclipse, the longest one of this century and visible in much of the world.

The so-called "blood moon," when it turns a deep red, was visible at different times in Australia, Africa, Asia, Europe and South America on Saturday when the Sun, Earth and Moon lined up perfectly, casting Earth's shadow on the Moon.

The lunar eclipse at around 4:00am on Saturday morning in Australia. ( Instagram: anthonyduffphotography )

The total eclipse lasted one hour, 42 minutes and 57 seconds, though a partial eclipse preceded and followed it, meaning the Moon spent a total of three hours and 54 minutes in the Earth's umbral shadow, according to NASA.

A bride poses for a photo during a lunar eclipse in Brasilia, Brazil. ( Reuters: Ueslei Marcelino )

A total lunar eclipse occurs when the Earth's shadow moves across the Moon, blocking out light from the Sun.

The Moon is framed by the Colosseum during a complete lunar eclipse. ( AP: Gregorio Borgia )

Perry Vlahos, president of the Astronomical Society of Victoria, said the eclipse offered a chance for reflection.

The Moon is seen through spires of the Duomo gothic cathedral in Milan, Italy. ( AP: Luca Bruno )

"What it actually shows is the solar system in action, and it gives you a bit of a better perspective of your own place in the scheme of things, in the universe," he said.

Lunar eclipse seen from The Gap in Brisbane. ( Instagram: nickgilpin )

Astrophysicist at the Australian National University Brad Tucker said a total lunar eclipse was something even experts got excited about.

The stages of the lunar eclipse as shot from Sydney. ( Instagram: dan.seto )

"The Moon passes into the Earth's shadow and that red colour really is the atmosphere of our Earth covering the light to bed.

"So you're actually seeing … the sunrise and the sunset of the Earth simultaneously," he said.

Australians saw the Moon turn red. ( Twitter: Scott Penny )

Andrew Fabian, professor of astronomy at the University of Cambridge, explained how the Moon took on the red hue.

"It's called a blood moon because the light from the Sun goes through the Earth's atmosphere on its way to the Moon, and the Earth's atmosphere turns it red in the same way that when the Sun goes down it goes red," he said.

Blood moon over Adelaide's SAHMRI medical research institute. ( Twitter: Ian Buckland )

Mars is currently traveling closer to Earth than it has since 2003, so some observers might have also seen what looked like an orange-red star, but it was in fact the Red Planet.

The Moon is seen during a lunar eclipse next to the Quadriga atop the Brandenburg Gate in Berlin, Germany. ( Reuters: Fabrizio Bensch )

Robert Massey, deputy executive director of the Royal Astronomical Society, said it was a "very unusual coincidence to have a total lunar eclipse and Mars at opposition on the same night".

The Moon turns red during a total lunar eclipse in Bernkastel-Kues, Germany. ( AP: Harald Tittel )

While this lunar eclipse was long, they can be longer — up to one hour and 47 minutes.

A view of the lunar eclipse from Waverly Cemetery in Sydney. ( Instagram: colindecosta )

The longest eclipse of the 20th century fell on July 16, 2000. It lasted one hour, 46 minutes and 24 seconds.

The Moon sets over Petronas Twin Tower in Kuala Lumpur, Malaysia. ( AP: Yam G-Jun )

The next eclipse to last that long will occur on June 9, 2123, but it will not be visible from Australia.

People watch the Moon rising behind the Temple of Poseidon in Greece. ( Reuters: Alkis Konstantinidis )

Rio de Janeiro's spectators cheered when the blood moon emerged from the fog.

Hundreds of people watched at a fort overlooking the iconic Copacabana Beach and Sugarloaf Mountain. The local planetarium set up telescopes for astronomy fans.

The Moon seen behind the Sheikh Zayed Grand Mosque in Abu Dhabi. ( Reuters: Christopher Pike )

"These telescopes are fantastic. It's one thing to see pictures of the planets in a book and another to see it in real life," said Ana Selma Ferreira, who brought her children to watch the spectacle.

Across Africa people turned to the sky, watching the reddish shadow slide up the Moon's surface. In Somalia, some hurried to mosques for special prayers.

In South Sudan, some dared to take photos in a country where using a camera in public is discouraged.

In Ethiopia's capital, Addis Ababa, people at an open-air restaurant admired a rare clear view during the rainy season, comparing a live NASA webcast to what they saw above. Then clouds rolled in.

North America missed out on the lunar eclipse but can look forward to the next one on January 21, 2019, according to NASA.

The Moon rises over Tel Aviv, Israel. ( AP: Ariel Schalit )

ABC/wires