Moonbows ~ Primary and secondary moonbows imaged by Paul Alsop near Thames on the North Island of New Zealand January 24, 2011.   ©Paul Alsop, shown with permission.


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"It was a stormy night. I went for a midnight walk to see what the sea was doing. I looked across the Firth of Thames and saw what I thought was just a weather front at first, but over a period of about 5 minutes the arc developed more into a moonbow. I ran back home to grab my camera and sure enough there is was. The light to the left is a bandstand and not a pot of gold!"

Moonbows have pots of silver at their ends.

Moonbows are rare. They need a bright moon less than ~35 high, a dark sky and a rain shower opposite.  Frequent showers interspersed with clear skies help. Hawaii, the Scottish Highlands and Isles and Northern Ireland are favoured places for lunar and solar rainbows New Zealand perhaps needs adding to the list.

Long camera exposures bring out the normal rainbow colours but to the unaided eye moonbows are ghostly objects with at most just a hint of colour (at right is an impression of the appearance). The colour receptors in our eyes are not sensitive enough in dim light.

A full moon is not needed for a moonbow. The Moonbow Challenge, to see a moonbow closest to New Moon, currently stands at 4 days 6 hours from new.