Mamaku resident snaps optical illusion ahead of blue supermoon

“It was just like this big glowing orange ball at the end of the street.”

These were the words used by Mamaku resident Sally Stewart to describe the phenomenon she saw on her way to work on Tuesday morning.

“I was just heading to work, and as [I came] up the rise, it was like, ‘Oh my God’,” Stewart told the Rotorua Daily Post.

“I thought I’d better stop and take a photo, because no one would believe me.”

Stewart, who works as a Hato Hone St John emergency medical technician, said the glowing orange ball had to be the moon, but meteors and aliens did cross her mind.

“Surely it was too big to be a meteor,” Stewart said.

“I did think about aliens, but I just watch too many [sci-fi] shows.”

University of Canterbury Mt John Observatory director Associate Professor Karen Rylvia Pollard said what Stewart had seen was an “optical illusion”.

“Usually, the moon looks redder when it’s closer down to the horizon,” Pollard told the Rotorua Daily Post.

“When the full moon is rising, at that point you’re looking through five or six times as much as if you were looking straight up.”

Mamaku resident Sally Stewart saw this on her way to work and took a photo. Photo / Sally Stewart

Pollard said the result of looking through the particles of the atmosphere was an optical illusion that made the moon look both larger and more red than usual.

But Pollard said keen stargazers would be in for a more amazing treat from tonight as a rare blue supermoon appears in the sky for the first time in 14 years.

“It should be really easy to see the supermoon,” Pollard said.

“It’s full and super-bright. So as long as you don’t have any clouds, it should be nice viewing conditions.”

There have been four supermoons in the night sky this year.

The supermoon will be just 357,181km away from Earth, making this the brightest of this year’s supermoons.

Pollard said the term “blue moon” meant the phenomenon was the second full moon to occur in a calendar month.

“That’s where the saying ‘once in a blue moon’ comes from.”

Pollard said usually, there were 29 and a half days between full moons. Tonight’s blue moon would be the last until sometime in the 2030s.

“It’s also a supermoon, so the moon will look a little bit brighter and a little bit bigger than it normally does. A supermoon is when the moon is slightly closer to the earth than average.”

And if you stay out a little later, Pollard said a pair of binoculars could help you spot a shining Saturn between 9pm and 10pm.

“Saturn is quite nice to look at at the moment,” Pollard said.

“And if you look slightly to the south you can see the Southern Cross, and if you look at the bright pointer, which is Alpha Centauri, you should be able to see that it’s a double star.

“Even with a small pair of binoculars, it’s fun to look.”

Pollard said that while the blue moon would occur at 1.35pm this afternoon the supermoon was a more gradual phenomenon.

“A supermoon just means the moon is closest to the earth. That doesn’t happen all at once. So the moon will still be quite close to us over the next few days.

“The moon should be impressive to see last night, tonight and tomorrow night.”

Correction: An earlier version of this article stated that the blue moon occurred on Wednesday night.