Wendelstein display, 24 Sep. 1997

This took place around noon local time in variable cirrus with a solar altitude of around 41 degrees. Notable features were a very bright Parry and upper tangential arc to the 22 degree halo and a highly coloured infralateral arc which was sketched but not photographed. There is some evidence for a Heliac arc in one of the photographs. The Wendelstein is a mountain SE of Munich at 47deg 43min N; 12deg 01min E.

Photographs taken on Fuji RHP transparency film with a Hassleblad and 180mm Sonnar lens, having a FOV 17 deg (24 deg diagonal). The original scans have been unsharp masked to enhance the faint details. The sketch shows the infralateral arc (referred to as a lower tangent) and what appears to be a Lowitz arc - although that does not appear in either of the photographs.

The upper tangent to the 22 deg halo is actually composed of a combination of the upper tangential arc - produced by horizontal column crystals - and Parry's arc - produced by similar crystals but with the top and bottom edge faces horizontal. These arcs overlap almost perfectly in the central region of photograph (b) but diverge slightly al the left and right edges producing an apparent smearing of the prismatic colours. This can be seen in the overlay of the simulation below. Although the cirrus structure is complex, there is evidence of a Heliac arc - produced by reflection in Parry-oriented crystals - cutting across the halo and tangential arcs in photograph (b). Again, this can be identified by looking at the simulation overlay. The position of this arc in azimuth is very sensitive to the solar altitude and can be used to determine the precise time the photograph was taken.

Click on the pictures for higher resolution (512 x 512) versions.

Wendelsteina_170 a, ~11:45 am

Wendelsteinb_170 b, ~11:50 am

Wendelstein sketch sketch of display made just after the photographs were taken

Simulations computed with HALO

W2_16M_over_170 Colour simulation movie (using pre-release Halo v3) with overlayed photographs.

Wendelsteinb_170_over Overlay of simulation on photograph b. Solar altitude: 41.2 deg. using Plate, Random, Horizontal column, Lowitz and Parry crystals.

Last update: 21 January 2002

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