The wonder of a moonbow

The hairs on the back of my neck prickled. I felt a tightening tension across the back of my eyes. I instinctively knew what was coming: a storm. One of those stunningly beautiful electrical phenomenon that pierce the mid-summer sky. For once I was grateful my old dog is no longer here, she hated storms (and the artificial firework version) with a fierce passion. Once in an attempt to escape the bangs and flashes, she had jumped the gate and run so far, so fast, that by the time we had caught up with her, she had worn away the pads on her paws. Most times when a storm hit she would pace the house, breathing heavily, looking for solace in human form, yet too restless to accept it when she found it. She left us more than two years ago.

Free to enjoy the storm (two untroubled dogs lie sleeping), I made my way to the top floor of our house, to our bedroom nestled under the roof. The windows open right out, allowing me to immerse my head into the night air. The air smelled fresh, the cooling rain landing in heavy sploshes. Such bright flashes, so high, and scattered across the sky. Bewildering – flash left, right, overhead, in front. Intermittent rumbles and cracks of thunder that seem unconnected with the flashes, no time to count between. Then I saw it. A silvery white arc in the sky. Was it a plume of smoke? Had one of the bolts struck home and caused a fire? No, it was unmoving, a beautiful, shimmering earthbound semi-circle, a bridge connecting sky and ground…

Flash! Briefly it revealed its multi-coloured form, then back to silver, again masking its brilliance. I stood transfixed, willing another flash… yes! And again! I could sense the storm moving further away across the fells. The arc dwindled from silver to soft grey, then faded out, it was gone. I stared at the space – nothing but a soft fall of rain and the outline of the fells against the night sky. Turning I moved to the skylight at the back of the room where the moonlight was flooding in. Gazing at it, I remembered hearing a voice on the radio informing me that it was near full. I noticed that the sky around the moon was uncluttered by clouds, sparkling with stars – no sign of the storm opposite. What a wonderful night sky, which left me questioning what it was I had seen. The next day, after searching books and using the internet I realised I had seen a lunar rainbow, also known as a moonbow. I found a poem by Robert Frost, Iris By Night (short extract below):

Then a small rainbow like a trellis gate, 
A very small moon-made prismatic bow,
Stood closely over us through which to go

If gold lies at the end of a rainbow, what treasure will I find beyond a moonbow? Only one way to find out – through the moonbow, that is the way to go…

Notes: A moonbow, also called a lunar rainbow, is a rainbow produced by light reflected by the Moon. The Moon itself does not emit light, moonlight is a mix of reflected sunlight, starlight and earthlight. Because moonlight is fainter than sunlight, moonbows are dimmer than rainbows.[i]

Moonbows may be found most often over waterfalls, particularly dramatic ones, with rapid flow resulting in spray. However the more transient, naturally occurring cloud based ones are very rare, difficult to predict, and require a specific combination of naturally occurring phenomenon: the moon must be very bright (full or near full), the rain must be opposite, the clouds dense enough to refract the light, but not so dark it obscures the view. It can be even more difficult to see colours in a moonbow – lightening from behind definitely helps with this!


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