I discovered this group while searching for a posting recently.
I don't think I posted their URL, so ...
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Dear Sky Watchers,
Lowitz arc halos were first drawn in 1790 but even in the
1990s their existence was doubted.
This month's Atmospheric Optics update gives current
views about these controversial halos. There is a gallery
of Lowitz images and a page with a different tilt on that
great St Petersburg display of 1790.