Somewhere over the moonbow

A moonbow above Hoopers Inlet on July 25. PHOTO: IAN GRIFFIN
A moonbow above Hoopers Inlet on July 25. PHOTO: IAN GRIFFIN
Compared to their daytime siblings, moonbows are rare, writes Ian Griffin.

Ian Griffin. Photo: Otago Museum
Ian Griffin. Photo: Otago Museum
A few weeks ago, I stood beside Hoopers Inlet. I hoped to witness an aurora that experts predicted might be visible. The night was cold, and the moon almost full. Cumulus clouds covered the sky while passing showers occasionally doused me and the new camera I was testing. 

In such conditions, rational human beings usually admit defeat, heading home to their warm house and an episode of MasterChef Australia. However, aurora chasers are far from rational. Our obsession with capturing the perfect picture of our elusive prey drives us to stay out when others are long gone.

After several hours of gazing at clouds, I noticed the sky was clearing. Stars could be seen through a growing gap in the southern sky. I focused my camera and, despite bright moonlight, began searching for signs of an aurora.

Unfortunately, none were visible. To make matters worse, it began to rain. I was cold and wet, and about to head home, when something genuinely astonishing appeared over the inlet. A moonbow!

Perhaps I’ve led a sheltered life, but until July 25, 2020, 54 years on this planet, I had never seen a moonbow. This is because compared to their daytime siblings, moonbows are rare, and can only be seen close to full moon. Like rainbows, moonbows are created when light passes through droplets of water. They are centred on the anti-lunar point in the sky, and, just like primary rainbows, have an angular radius of 42 degrees with red on the outside and violet on the inside.

William Wordsworth famously wrote that ‘‘My heart leaps up when I behold a rainbow in the sky.’’ I wonder what he would have made of a moonbow. He would have certainly done a more poetic job than I in describing its beauty. Kai Tahu call the aurora ‘‘Nga kahukura o hine-nui-te-po’’, which means ‘‘the rainbow of the goddess of the night’’.

It is ironic that on a night I was hunting one rainbow I got to enjoy another!


 

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