Northlanders can see super blue blood moon eclipse - if sky cloudless

The moon, seen here over Whangarei on Saturday night, will be a rare phenomenon overnight tonight - a supermoon, a blue moon and a total lunar eclipse - for the first time since 1866. Photo / John Stone

Northland skywatchers will be in for a rare celestial phenomenon in the early hours of tomorrow, if the clouds stay away for it to be observed.

It will mean getting out of bed very early - or staying up very late - with a very rare "super blue blood moon eclipse" visible above New Zealand on February 1 at 2.30am.

It's the first time the three celestial events - a supermoon, a blue moon and a total lunar eclipse - have occurred at the same time since 1866.

A supermoon is when a full moon coincides with the closest the moon gets to Earth during its orbit and appears bigger and brighter. A blue moon is when two full moons occur in a single calendar month.

The third simultaneous phenomena to occur is a total lunar eclipse, also known as a blood moon, when a full moon, Earth and the Sun line up and the moon appears to be red. And while it's a once in several lifetimes event, observing the "super blue blood moon eclipse" is very much dependent on the weather.

The forecast is for rain tonight/tomorrow.

Peter Felhofer, president of the Northland Astronomical Society, said the moon would be a spectacular sight for those who did see it.

He said in New Zealand the moon was technically not a blue moon because it occurs about 2.30am on February 1, but for the rest of the world it is. He said this might be splitting hairs, but there was still plenty to get excited about.

''It's particularly exciting that the lunar eclipse is happening on a super moon and the moon is expected to be anything from a deep red to purple, so it should be quite a sight for those who do see it."

But compounding the situation further than the possible cloud dolour is that it can be hard to spot the moon when there is a lunar eclipse," Mr Felhofer said.

''Normally you'd look for the biggest bright thing in the sky, but it's going to be dark and if the moon is purple it will be very hard to spot in the night sky

''But it will be going for a long time, with the first sighting just before midnight then it is entering the umbra [shadow of the Earth] about 1.30am. Then after 1.30am it goes into the full umbra and at 2.30am it will be right in the middle of the eclipse.''

He said if a person stood facing north they should look straight up in the early hours of tomorrow morning for the best chance of seeing the rare event.