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There’s a big red moon on the rise tomorrow night right across Australia, so grab your cameras and head outside if the weather is clear.

The heavens are lining up in the first total lunar eclipse to be seen across Australia since July 2018.

And this lunar eclipse also just happens to occur shortly after the Moon is closest to Earth (perigee), so that makes it a blood red “supermoon” (or a perigee-syzygy eclipse, if you want to use the astronomical term).

All Australians will have the chance to see the most spectacular parts of the eclipse.

Astronomer Andrew Jacob says it should look beautiful, no matter if you are in the east or the west of the country.

However, with the eclipse happening at exactly the same moment wherever you live, those views will be very different.

From his vantage point at Sydney Observatory, Dr Jacob will get an iconic view of the Moon changing colour high up in the easterly night sky, from 7.44pm Sydney time.

“We’re expecting it will rise from the area above the Opera House, so we’ll see if we can get some shots of that,” he said.

Lunar eclipse moon next to the Sydney Opera House

Getty images: Peter Parks/AFP

Over in the west of the continent, the Moon will be changing colour as soon it rises above the horizon, just after sunset from 5.44pm Perth time.

“If you were looking for a photographic moment or best experience of a moonrise, then perhaps Perth is getting the best of it,” Dr Jacob said. 

The Moon there will look super big thanks to a visual trick  — known as the moon illusion — which alters your perspective of its size when it’s close to the horizon.

And its red colour will likely be enhanced by dust in the atmosphere, much like the colours in a sunset.

What is a lunar eclipse anyway?

A lunar eclipse occurs when the Moon is directly opposite the Sun – aka full Moon.

It doesn’t happen every full moon — only when the Moon’s orbit is aligned so it passes through some part of Earth’s shadow.

Illustration of what happens during a lunar eclipse.

ABC: Julie Ramsden

Just what the eclipse looks like and how long it lasts depends on which part of the shadow the Moon glides through and how fast the Moon is moving.

When the Moon moves through the deepest part of the Earth’s shadow (the umbra), it takes on a distinctive red glow — an effect caused by the bending of light in Earth’s atmosphere.

This can be seen in a partial eclipse, when some part of the Moon has moved into the shadow, but it is more prominent during a total eclipse, when all of the Moon has moved into the umbra.

When is the best time to see the eclipse?

The eclipse will be visible from Australia, New Zealand, the Pacific, South-East Asia and parts of North and South America at the same time.

But not all of those locations will see the whole eclipse, and some parts of the world won’t see it at all.

“A lunar eclipse only takes a few hours to occur from the very beginning to the very end,” Dr Jacob said.

“During that time, the Earth has rotated but it hasn’t done a full 24-hour rotation, so there will be some parts of the world for whom the Moon is below the horizon for the entirety of the time.”

Luckily, everyone in Australia is in the box seat for the main event.

10:52pm

Moon aficionados in the eastern states may also be able to see faint traces of the penumbral eclipse —  as the Moon glides through the outer shadow of the Earth, before the umbral eclipse begins.

The penumbral eclipse won’t be visible from Western Australia, because the Moon is already passing through the umbra as it rises above the horizon.

“Due to the light of the sky and the bright light of twilight, people in WA pretty much miss the penumbral phase [at the beginning],” Dr Jacob says.

Phases of lunar eclipse

Getty Images: Hande Feng

How long will it last?

This eclipse takes about three hours to complete, from the time the edge of the Moon starts passing through the umbra until the end.

But you have to get your timing right to see the Moon at its reddest.

The total eclipse phase will only last about 14 minutes.

That’s relatively short in total eclipse terms (but not the shortest this century).

“This particular one is short because … [the Moon is] moving through the very edge of the shadow,” Dr Jacob said.

And the Moon will spend less time in the shadow because it’s travelling slightly faster than average.

“When [the Moon] is closest to us, it is moving at its fastest speed [in its orbit],” Dr Jacob explained.

And, although we like to call eclipses “blood red moons”,  this one is probably going to be more of a russet moon because it’s passing through the outer edges of Earth’s shadow.

“I would expect it’s going to have a reddish tinge, but that may be a gradient across the Moon as well,” Dr Jacob said.

Will the eclipse look extra big because it’s a supermoon?

Although the Moon can look full for a couple of days, in astronomical terms a full Moon happens at a very specific point in time, wherever you are in the world.

This full moon (and eclipse) also happens to fall nine hours after the Moon has reached its closest point to Earth this month (357,311 kilometres away), so it is a supermoon.

A man stands on the horizon, completely silhouetted by the moon, in sand dunes in Lancelin. January 31, 2018.

ABC News: Andrew O’Connor

There are a number of definitions of a supermoon (a phrase that was originally coined by an astrologer).

Some people say a supermoon is any full or new moon that occurs within 24 hours of it making its closest approach to Earth (perigee) that month, while others say it’s when the full moon comes within 360,000 kilometres of Earth.

This moon meets both those definitions, but in reality this will not change your view of the eclipse at all – it’s near impossible to tell the difference between a normal full moon and a supermoon.

But if you look at it near a horizon or next to a building, it will look super thanks to the moon illusion we mentioned above playing tricks with your brain.

Harness the moon illusion combined with a telephoto lens for a top shot.

How often does a blood red supermoon happen?

A blood red supermoon sounds exotic, but it’s only been a little more than three years since the last one in Australia (and that was a “super blue blood moon” in all states except New South Wales, if you want to go the whole hog with names).

The frequency of this event happening depends upon the intersection of celestial movements, and depends on which definition of a supermoon you use.

On average there are between two to three lunar eclipses each year.

But they are not always total. Depending upon the alignment of the Moon and the Earth, they may be only partial or penumbral eclipses.

And only people living on the night-time part of the Earth get to see some or all of the eclipse.

For example, most of North America only saw a partial eclipse in January 2018.

But they got to see a great total eclipse in January 2019. This total eclipse, which we missed out on, was also a supermoon.

Supermoons are pretty common. 

Depending upon your definition, there are between two and four supermoons a year.

“I’ve made up my own definition of when the full moon is close to the perigee and I ended up with nine supermoon eclipses in the next 10 years,” Dr Jacob says.

But not all of these will be total eclipses, or visible from Australia.

If you want to be a stickler for the 24-hour rule, the next super blood red full moon to grace Australia falls on October 8, 2033.

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