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Hello Mark and other list members,
Thank you Mark for interesting story about Hevel's display.
Mark Vornhusen wrote:
| Fehlau describes the 90 deg halo based on Hevel with these words: "...
| On this circle (comment: parhelic circle) stood three silver suns. One
| in the northwest opposite of the sun, one in the northeast and one in
| the southwest. Through the two last gone a piece of a white circles arc,
| comming from the top. So that it seemed that there was a white cross
| going through the two white parhelia. This cross was very marvelous and
| was visible for 1 1/2 hours."
| Hevel also mentioned that the pieces of the circle formed a cross with
| the parhelic circle. A subhelic arc cuts the parhelic circle under a
| small angle and can`t look like a cross. This is an argument against the
| opinion, that Hevels halo was a subhelic arc.
I think that these "white cross going through the two white parhelia"
could be
explaned with pillars going through 120 degree parhelia. This 120 degree
pillar
can be quite bright and long vertical columns. Several photos about these
120d
pillars are known. To put this 120 degree parhelia in a wrong atzimuthal
angle
is very common error. You are right, it doesn't sound like a subhelic arc.
| Fehlau writes that the whole city talked about the sky appearance in the
| last 14 days, still talkes about it and will talk about it in future. At
| the end of his writing a drawing of a halo display can be found. He did
| not mention this drawing in the text. So it is unsure if this is a
| drawing of the Danzig display. It is different form Fehlau`s description
| of the phenomenon. I make this drawing temporary available for you on
| this site: http://members.tripod.com/~regenbogen/hevel.jpg .
Interesting point is that in this drawing those arcs are almost (angle is
a
little bit too big) like subhelic arc when sun elevation is about 27
degree. At
that sun elevation subhelic arc is going through 120 degree parhelia. Full
22
degree halo is visible in this drawing and that's why sun elevation must
be
something like that. Well, this drawing is not fully accurate: sun dogs
should
be clearly away from 22d halo when full 22d halo is visible (maybe this
drawing
is covering a long period of time). Also those two "hevel's halos" are in
different atzimuthal angle.
You are right that we can't be sure if this drawing is about the same
phenomenon what is in Hevel's more famous drawing (I think that it
probably
is). If this drawing is from the same display, I would say that the
subhelic
arc-explanation seems to be even more convincing now.
| Regards,
| Mark Vornhusen
Regards,
Jarmo Moilanen
current leader of Finnish Halo Observing Network
| 