A spectral halo with an angular radius of about 46º occasionally seen in a cirrostratus around the sun or moon. Like the 22º halo, it is caused by refraction through randomly-oriented ice crystals and is sometimes accompanied by sun dogs - brighter, more colourful patches at or just outside its edge.

The 46º halo is much rarer and fainter than the 22º version: It is only seen when the ice crystals are just right. Either kind of halo is a sign of low pressure coming in, and often means there is rain and other wintry weather on its way.

To more aerial spectra...

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