Lunar Aureole

Juha Ojanperä (site) produced this HDR image of a lunar aureole/corona seen in Seitseminen National Park, Finland.   Low level fog/stratus was responsible. The image nicely captures the visual appearance and spirit of the scene.   ©Juha Ojanperä.

Atmospheric
Optics
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A corona and aureole is only a part of the complex pattern that scattering and diffraction by fog and cloud droplets weave around the sky.

At left, Philip Laven's MiePlot program computes the light scattering by 100 micron dia. droplets all the way from the sun or moon to the antisolar (lunar) point directly opposite.

Light is scattered in all directions. The vertical scale is logarithmic and each division 10X. The range of scattered brightness is enormous. The barely deviated rays (waves) of the corona are the most intense.

The fogbow's primary, secondary and supernumeraries show up in the opposite hemisphere. Directly opposite the light source is the glory.

The two components of polarised light are shown. We see that the corona is unpolarised. The fogbow (like the rainbow) is strongly polarised. The glory is polarised in a complicated manner.