A halo feature is a group of optical phenomena in the form of rings, arcs, pillars or bright spots, produced by the refraction or reflection of light by ice crystals suspended in the atmosphere, like in Cirriform clouds, diamond dust, etc. Most common is the 22° ring halo, followed by parhelias (sun dogs) and tangent arcs. Quite rare is the Parry arc, which may occur as 'suncave' or 'sunvex' depending whether it occurs as concave or convex with respect to the sun, and this in relation to the elevation of the sun above the horizon: below 15° elevation the convex form can appear. This halo is to be found above the upper tangent arc.

The picture was taken on a sunset with the quite common upper tangent arc (lower halo) and the very rare sunvex Parry arc (upper halo), giving the appearance of a "double V" halo, visible for a couple of minutes.