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| Lunar Corona ~
Imaged from the Sierra de Madrid, Spain by Dani Caxete (site). The bluish white glow surrounding the moon is the corona�s central aureole. Its edge is straw coloured merging to reds. Out at upper right are the greens and yellow reds of the first diffraction ring. Moon coronas look like this to the eye. To capture this visual impression on camera takes a fortuitous cloud to dim the moon and photographic skill. All images ©Dani Caxete, shown with permission |
| This more 'usual' corona photograph shows the diffraction rings and their delicate colours to greater perfection but at the cost of .overexposing the moon. |
The change in droplet size at the cloud edge has greatly distorted the rings. We see the transition to cloud iridescence. |
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| IRIS Mie scattering calculations for monosized drops at left and ones with a 20% standard deviation Gaussian distribution of sizes at right. The greater the spread in droplet sizes, the fewer the rings. |
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| Coronae arise from diffraction of sunlight or moonlight by clouds of randomly spaced water droplets. Not evenly spaced as claimed in this Univ of Illinois howler! Each droplet produces its own diffraction pattern. And what we see in the sky is a sky transform - the collective diffraction glints from millions of drops. |
