Thursday 22 April 2010

Lowitz arcs on old film photographs

Last weekend, I visited my parents in Normandy. I took advantage of my visit to dig through my old astronomy journals of observations and pictures. I was looking for my records of what has been my best halo display. In my memories, it consisted in extremely bright left parhelion, bright circumzenithal, and a combination of suncave Parry and upper tangent arc.

I found my record, sketch ( <a href=" http://www.ursa.fi/blogit/media/blogs/halos/Lefaudeux/18-09-98-17h15-17h55HL_post.jpg">1 ) and pictures ( 2 - 3 - 4 ), and realized there were very prominent Lowitz arcs too!

From my notes, the display happened on September 18th, 1998, between 17h15 and 17h55 local time. The sun was at 24 degrees altitude at the middle of the display. At that time, I had little knowledge of the halos. I just knew from astronomy books about parhelia, 22° and 46° halos. I had observed before upper tangent arc (which I called upper 22° parhelion) and circumzenithal arc (which I called upper 46° parhelion), but never Parry arc.

During the display, I was mesmerized by the colourful upper suncave parry arc and by the parhelion brightness. My notes are focused on these arcs, especially the Parry one, with detailed description of its length, width, brightness and colors. Nothing on the Lowitz arcs except the sketch which shows radiating arcs from parhelia.

The stitched picture shows almost complete upper Lowitz arc, very long Parry arc and faint 22° halo. There are also some weird bands on the bright parhelion. I think I have some memories of shadow bands running across the parhelion, a bit like in the video by Anna Herbst ( <a href=" http://spaceweather.com/swpod2010/11feb10/anna-herbst1.mov?PHPSESSID=liolll4f05nuq4m9ascc45gpg5">5 ), but cannot be sure as there is no mention of these in my notes.

I really wish I could observe again such an exceptional display now that I am able to appreciate it to its true worth

Nicolas Lefaudeux
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6 comments:

  1. marko22 April 2010 at 09:36

    Here is simulation. The labels refer to the upper, lower and circular Lowitz arc components. Spinning orientation was used.

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  2. jukka ruoskanen22 April 2010 at 09:52

    Wau! Old records are worth going through! Nice display indeed.

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  3. Michael23 April 2010 at 01:45

    Thats a good one there I like the upper parry and lowitz arcs the best. I've been an active halo observor since childhood but never kept records until I got my first camera in 2000. Since then I have seen many great displays and some extreme rarities like wegener arc, helic arc, tricker arc, and stuff like elliptical halos as well

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  4. marko23 April 2010 at 15:39

    Here we have, not necessarily the best photos of Lowitz arcs, but the best photographed Lowitz display. There is no 22 halo here to mix things up.

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  5. nicolas lefaudeux23 April 2010 at 21:06

    thanks a lot! unfortunately the photographs are not at the level of the display, and I had to salvage one of the picture which suffered strong light leak during the developping process :-(

    from what I have seen on this blog and on the internet about halos, it looks like the best Lowitz displays occur in high cloud while for other halo diamond dust are best. is there any known reason for that?

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  6. marko riikonen24 April 2010 at 09:21

    There are some good ones in diamond dust as well, concerning the circular component. Other components are difficult to distinguish because sun is usually low and parhelia is near the 22 halo.

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