On an evening walk in the autumn of 1799, William Cole, a now forgotten English poet, was suddenly stopped in his tracks by a sublime appearance in the darkening Norfolk sky above him – a vision so extraordinary he was moved to record its aerial rhythms in rhyme: “The atmosphere with humid vapours flow,/And the pale moon displays her lunar bow.”

Aware that readers of his poem would probably be mystified by the atmospheric event he described, Cole appended a footnote, directing readers to an article in a local newspaper corroborating what he’d witnessed: “See the Norfolk Chronicle of Nov. 17, 1799”.

Two hundred and seventeen years after Cole’s encounter, fresh sightings of the strange lunar bow (sometimes referred to by meteorologists as a ‘moonbow’) are once again in the news. A pair of ethereal photos captured recently in Yorkshire and in Northumberland have projected their luminous magic across social media this week, introducing Twitter and Facebook followers around the world to a heavenly phenomenon that many had previously never heard of, let alone seen.

Generated in the same way that its more common cousin, the rainbow, is produced, a lunar bow occurs when light (this time reflected from the moon, rather than shining directly from the sun) is refracted through rain or mist suspended in the dimming atmosphere. Much more delicate in its fleeting projection than a rainbow, the lunar bow rarely conjures the full spectrum of colours and typically appears an icy white.

Given its ghostly allure and spectral charm, one might have thought that the moonbow was an ideal subject for artists keen to avoid slipping into rainbow kitsch. A comment by the English landscape painter John Constable, who characterised the lunar bow as “that most beautiful and rare occurrence”, suggests that artists have indeed been well aware of its appeal. So it is surprising to discover that, apart from a notable canvas by the German Romantic painter Caspar David Friedrich, the moonbow has by and large escaped the eternalising alchemy of art.

In Friedrich’s Mountain Landscape with Rainbow (1809-10) – sometimes given the subtitle Landschaft mit dem Mondregenbogen or Landscape with Moonbow – a resplendent arc cuts through the lustrous darkness in which a weary wanderer has paused, as if weaving a protective dome over him. In a time of terror and ever-refracting global uncertainties, it is not surprising that real-time echoes of Friedrich’s consoling vision, captured by contemporary photographers, are once again causing a soulful stir.

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