2006. január 27., péntek

44° parhelion in Finland

Once thought to be an extremely rare halo, the 44° parhelia is now increasing it's appearances. The display on the right was photographed by Jaakko Tähti on 21. December 2005 at Viitasaari, Finland. To my knowledge, this is the eight photographed occurrence of 44° parhelion.

The formation of 44° parhelia differs from other halos in that it's not caused directly from sun rays, but from light rays of another halo - namely the common 22° parhelia. In other words, it is the parhelia of parhelia. Formation of 44° parhelia seem to require diamond dust conditions and very bright 22° parhelia. According to Jarmo Moilanen, also low sun elevation is essential to ensure there are enough ice crystals between the sun and observer. Here the sun elevation is 2°.

List of photographed occurrences of 44° parhelia:

1 megjegyzés:

  1. Jaakko Tähti deserves congratulations!

    For completeness of the records, the Minnesota display was on 3rd January
    2004. A low sun display. Bright left and right hand 44° parhelia were photographed. The 46° halo was bright and this allows the precise angle of the parhelia to be measured by comparison of their position with that of the 46° halo.