This interesting coloured arc was observed early this evening from my back yard as high cirrus cloud was moving in from the west. At the leading edge of the thicker cloud in the centre of the photograph you can just make out a 'smiling' curved rainbow of colour that stretches across the width of the image. The colours, from top to bottom, appear to be violet, blue, yellow, orange and red, typical of a rainbow.

From the fact that the sun was below this arc in the sky and the way the arc appears to curve away from the horizon, I suspect that this is an example of a circumzenith arc formed as sunlight is refracted by ice crystals high in the atmosphere.

The picture was taken at 19:06 BST from Roseburn, Edinburgh on a Canon A640 digital camera.