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A moonbow is uncovered

Published on 23 January 2010 by in Features

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George Peacock’s hand written description of the lunar rainbow that occurred on Saturday June 9 1849 (Image: Derek Reid). Click to expand.

George Peacock’s hand written description of the lunar rainbow that occurred on Saturday June 9 1849 (Image: Derek Reid). Click to expand.

PhD student Linden Ashcroft came across a rare meteorological phenomenon when looking through some early instrumental data given to the SEARCH project by a former CSIRO scientist Derek Reid.

Derek Reid

One of the scientists who conducted pioneering research into early instrumental data in Australia was Derek Reid. Before his retirement from CSIRO in 2008, Derek conducted an extensive search into potential data sources.

He  kindly provided his findings to the SEARCH project, in the hope that we will be able to make use of them.

Included in these findings are some images of handwritten, daily weather observations taken in 1849 by observers in Port Phillip, Port Macquarie and Port Jackson (South Head). These meteorological stations were set up by the NSW Governor at the time, Sir George Gipps, and were manned by trained convicts.

George Peacock

The observer at Port Jackson, in Sydney was George Edward Peacock. An attorney, Peacock was sent to Australia in 1837 under a life sentence for forgery. While he was more famous for his oil paintings of the Sydney region, Peacock also kept the meteorological journal at South Head from June 1841 until December 1855.

The meteorological journal contains four-times daily observations of temperature and pressure, as well as daily wind direction, rainfall and general comments. One of these general comments, nestled among all the numbers, is a description of a lunar rainbow that occurred on the night of Saturday June 9 1849.

In a special note attached to the journal, Peacock obviously felt the phenomenon was worthy of particular mention. He writes:

Immediately after the moon shewed her head this night above a low bank of clouds in the eastern horizon, that rare and striking, but somewhat ominous phenomenon, a Lunar Rainbow, was presented in the western sky; the who arch was exhibited in perfect beauty; the lower extremities, particularly the Northern one, reflecting most distinctly the prismatic colors, excepting the yellow, which appeared softened into a silvery white.

The Bow remained in a perfect state for 8 or 20 minutes, then partially disappeared – again became perfect, – and thus fluctuated for about half an hour.

I have seen several lunar rainbows, but never so perfect a one as this.

Lunar rainbows, or moonbows, are rainbows caused by the refraction of moonlight through rain droplets.

Lunar rainbow are very rare as the moon has to be quite full and low, the sky needs to be dark and rain needs to be falling opposite the moon.

It seems as though conditions were perfect. The weather on the 9th, and for two days after that. was described by Peacock as “dirty…squally weather” with rain falling on the 9th, 10th and 11th.

This beautiful moment, captured in detail by Peacock, is just one striking example of the events that can and hopefully will be uncovered by searching through weather observations of the past.

The Heads of Port Jackson N.S.W. from off the North Head - a squall, 1846 painted by G. E. Peacock

The Heads of Port Jackson N.S.W. from off the North Head - a squall, 1846 painted by G. E. Peacock. Image: State Library of NSW

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