Keen astronomers to gather at Whanganui's Ward Observatory for rare 'blood supermoon'

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Keen stargazers are invited to gather at Whanganui's Ward Observatory on Wednesday evening to witness a rare space phenomenon New Zealand hasn't witnessed in decades.

The observatory will be open from 10pm to witness the rare "blood supermoon", a rare combination of three factors: a full moon, the moon being at its closest point to Earth in its orbit (supermoon) and a total lunar eclipse.

The last time all three of these occurred in New Zealand was more than 40 years ago in 1982.

Whanganui is forecast to be one of the best places in New Zealand to view the super blood moon.

The telescope at Ward Observatory is the largest unmodified refractor telescope still in use in New Zealand. Photo / Bevan Conley

Wanganui Astronomical Society president Ross Skilton said the moon would be "significantly red" from 11.10pm to 11.25pm as Earth passes directly between the moon and the sun.

The total lunar eclipse, also known as a blood moon, occurs when Earth lines up between the moon and the sun, hiding the moon from sunlight and blocking most of the blue light. The remaining light refracts onto the moon's surface causing a red glow.

A supermoon occurs when the moon is at its closest point in its orbit around Earth, making it appear larger than usual.

"Supermoons occur every circuit of the planet," Skilton said.

"It just so happens this has occurred at the same time as a full moon and a total lunar eclipse.

"The red colour is due to the Earth blocking the sun's light and only filtered light can reach the moon."

He said there would be a variety of telescopes and binoculars available at the Ward Observatory for keen viewers to use.

"It should be a pretty special evening."

According to Niwa's forecast models, Whanganui skies look to be mostly clear, with cloud being the only potential obstacle for viewers.

Skilton said any updates about the event would be posted on the Wanganui Astronomical Society Facebook page - www.facebook.com/WanganuiAstronomicalSociety.