Oslo, Norway ~ December 16, 2007

The diamond dust display covered a wide 30-40 km
area. Johannes Lillegaard took the three images at top showing its main aspects; a dominant "V" shaped upper tangent arc, bright sundogs, a 22° halo, a parhelic circle and upper and lower sun pillars. Further from the sun, a colourful supralateral arc and a 46° halo shone.

There were other halos. A rare Moilanen arc was seen in one location. A bright sunvex Parry arc sat close above the upper tangent arc. From high ground and close to sunset the diamond dust created a lower tangent arc and subparhelia.
Moilanen arc - Steinar Midtskogen captured images 4 and 5. The lower one shows a rare Moilanen arc - the "V" shaped arc above the sun and halfway towards the 22° halo. The arc was possibly made by crystals nucleated by ski-slope snow machines 1.5 km to the north.
Parry arc - Signe Strøm Flugsrud's images (6,7) show the "V" shaped sunvex Parry arc above the upper tangent arc and mirroring its form.

Supralateral arc & 46° halo - Image (7) and that that of Odd-Tore Saugerud (8) reveal that the outer arcs twice as far from the sun as the 22° halo were a combined supralateral arc and the more rarely seen 46° circular halo. The supralateral arc always touches the (upward curving in images 7,8) circumzenithal arc. The lower arc is the 46° halo.   Its separation from the supralateral arc varies with solar elevation and the low sun presented
a good opportunity to see them spaced
well apart.
Subhorizon arcs
Odd-Tore Saugerud captured these very low sun halos at Kolsås near Oslo. Diamond dust in the valley shows the lower half of the 22° halo and the narrow inverted V of a lower tangent arc. Above it is a narrow and intense lower sun pillar. The arms of are subparhelia link upwards to the sundogs.
Images (1)(2)(3) ©Johannes Lillegaard - Images (4)(5) ©Steinar Midtskogen, (6)(7) ©Signe Strøm Flugsrud, (8)(9)(10) ©Odd-Tore Saugerud.