Sunday, 7 June 2020

A possible surface 28 halo

On 14 March this year in Tampere, on lake ice that was covered with thin snow a 22 halo was visible. Its glitter was not that bright, likely because of small crystals. But the glitter was relatively dense. Because the inner edge of the halo was not well defined, I took a long photo series as I have linked this impression to odd radius halos. I snapped photos for 23 minutes duration and after rejecting a few frames the stack had a total of 290 frames.

I made different versions of the stack that were adjusted with Photoshop. They are shown here in non-mirrored - mirrored pairs:

pair 1: double usm + HDR Toning
pair 2: background removal (BGR) + HDR Toning
pair 3: background removal (BGR) + HDR Toning. BGR with different values than for pair 2
pair 4: BR + BGR 

It seems this was an odd radius display. A weak 24 halo appears to show up in pairs 2 and 4. Images also seem to have 35 halo. The most interesting thing, however, is the feature that looks like 28 halo. I measured it from BR image using a star field photo and the inner edge was at 27 plus some. Also, I measured the apparent 35 halo and got 35 degrees.

The night's lowest temp was at the sunrise, -7 C at the airport. Windy, clear skies overnight. Not quite the foggy, calm conditions that I have previously associated with surface odd radii. Unfortunately I forgot to take the microscope as I headed for the lake with bicycle. Realized this pretty soon after leaving my place, but didn't turn back.

This is not the first suspected surface 28 halo. On 7 April 2012 Jari Luomanen and I photographed on a small lake in Eastern Finland an odd radius display that by all looks has a 28 halo:


  1. Hope to see an odd radius display with 28d halo some day

  2. Keep the convex mirror around if you really want to see it with your own eyes. At Lascar we actually saw the 28 halo through mirror. I thought of it then as 24 halo, which probably goes down to plain stupidity.