Upper Lowitz arc, San
Francisco imaged on
17th November 2006 by Mila Zinkova. ©Mila Zinkova,
shown with permission.
The arc is apparent as the bright 10
o'clock 22° halo region and possibly above.
over for an enhanced view.
Arcs like this could be produced by
column crystals rocking about a Lowitz axis perpendicular to the long
'c' axis as suggested by Riikonen et.al.