It can be a challenge to identify an atmospheric optical effect when the ice crystals refracting the sunlight to make it appear are only in certain parts of the sky. Though the shape and colours might appear as a clear arc or halo when ice crystals cover the sky in the form of the high layer cloud Cirrostratus, only fragments of it will show when the crystals are in isolated patches. This was the case when Liz Danzico (Member 64,870) pulled over in Springfield, New Jersey, US to marvel at a sky ‘peppered with clouds of different colors and shapes’.

Liz had spotted a circumhorizon arc – or at least parts of one. If the whole sky had been covered in a Cirrostratus cloud made of the right sort of ice crystals (shaped like hexagonal plates), the light effect would have appeared as a broad, horizontal, flat band of colours ranging from red at the top to blue at the bottom, low in the sky beneath the high, high Sun. But the ice crystals forming Liz’s circumhorizon arc were in Cirrus clouds that covered just patches of the sky. Only fragments of the optical effect could appear. But oh, what fragments! ‘We couldn’t believe other drivers weren’t pulling over as well to get a view of this rare sight!’ said Liz. ‘For what seemed about a half hour, clouds everywhere you looked shone blue, pink, yellow, and more, against the deep blue sky.’