Many Australians out trick-or-treating for Halloween will be able to catch a glimpse of a super rare blue moon on Saturday night.
A blue moon does not refer to the colour but is rather a quirk of our calendar months.
Usually there are 12 full moons in a year but every so often there will be 13, meaning that in one month there will be two full moons.
Western Australia will be the only state to see a blue moon tonight which will occur at 10.49pm on October 31.
In the other states it will fall on November 1 meaning that they will miss out on the blue moon.
Tonight's moon will be the smallest of the year, with Halloween coinciding with a 'minimoon' - where the moon is at its furthest point of orbit from the sun - also known as an apogee moon.
Many Australians out trick-or-treating for Halloween will be able to catch a glimpse of a super rare blue moon on Saturday night (pictured: the full moon over Narrawallee Beach on the south coast of New South Wales on June 6, 2020)
The full moon phase, which is the lunar orb's position in in orbit, begins on Saturday night for Western Australia but will be early on Sunday morning for the rest of Australia
A blue moon is blue in name only - actually referring to the second full moon in one calendar month (pictured: the moon over Sydney in 2016)
AUSTRALIA'S FULL MOON ON OCTOBER 31
Western Australia
10:49pm AWST Oct 31
New South Wales
01:49am AEDT Nov 1
Australian Capital Territory
01:49am AEDT Nov 1
Northern Territory
12:19am ACST Nov 1
Queensland
12:49am AEST Nov 1
South Australia
01:19am ACDT Nov 1
Tasmania
01:49am AEDT Nov 1
Victoria
01:49am AEDT Nov 1
Australian timezones will prevent the eastern states from experiencing the same phenomenon - being roughly one to two hours ahead of WA.
The moon will reach its fullest early on Sunday morning for the rest of the country, however, they too will be able to see a blue moon when the moon cycle's to its full point again on November 30.
Many other parts of the world will also see the blue moon on October 31 with the next one not appearing on this date until 2039.
The last time the spectacular cosmic display happened on Halloween was in 1944.
People in North and South America will have a glimpse of the Blue Moon, along with those in India, Europe and Asia.
The idea of a Blue Moon as the second full moon in a month comes from an article in the March 1946 issue of Sky and Telescope magazine.
This issue published an an article called Once in a Blue Moon by James Hugh Pruett, who referred to the 1937 Maine Farmer's Almanac, but with a simpler definition.
'Seven times in 19 years there were – and still are – 13 full moons in a year,' he wrote.
'This gives 11 months with one full moon each and one with two.'
'This second in a month, so I interpret it, was called Blue Moon.'
NASA shares that this is also deemed the Hunter's Moon, the full moon that follows the Harvest Moon that appeared on October 1.
A full moon rises above the Sydney Opera House . A full moon will be visible in the city early on Sunday morning
'According to the Farmer's Almanac, with the leaves falling and the deer fattened, this was the time to hunt. Since the harvesters had reaped the fields, hunters could easily see the animals that have come out to glean (and the foxes that have come out to prey on them),' reads NASA's statement.
'The earliest use of the term 'Hunter's Moon' cited in the Oxford English Dictionary is from 1710.'
On Halloween night, Jupiter will appear in the southwest and Mars will shine brightly in the east-southeast.
Astronomers have said Mars is particularly good to look at through a telescope from Australia in at the moment - with remnants the polar ice caps visible.
The planet is currently visible as a bright orange spot just above the eastern horizon in the early evening.
The idea of a Blue Moon as the second full moon in a month comes from an article in the March 1946 issue of Sky and Telescope magazine (pictured: October's blue moon over Russia)