1. skephu

    skephu Senior Member

    Patrick Roddie of San Francisco has posted this video showing a strange double halo:



    [​IMG]

    What is this? I can't find anything like that in the atmospheric optics resources.
     
    Last edited by a moderator: Feb 24, 2016
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  2. Mick West

    Mick West Administrator Staff Member

    Fascinating. He also posted this photo:
    12747317_10156673186705595_885318669297130752_o.

    Detail, contrast enhanced.
    20160224-161436-qs9d4.

    It appears to be a solar corona, possible with a 22° halo in the mix. Edit, now it appears to actually be an additional halo.


    http://www.atoptics.co.uk/droplets/corona.htm
    [​IMG]
     
    Last edited: Feb 24, 2016
  3. skephu

    skephu Senior Member

    Oh. Do you recognize that line-shaped cloud in the photo?
    It's the one Marin B posted in the other topic. At least it's extremely similar.
     
  4. Mick West

    Mick West Administrator Staff Member

    Very similar!

    20160224-165351-kze2k.
     
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  5. skephu

    skephu Senior Member

    Here's a heavily color-enhanced version:
    upload_2016-2-25_2-19-23.

    I think the inner, smaller ring (or rings) may be a corona. But the two outer rings seem to be too large for that, their edges are too sharp for a corona (and the spacings and the colors don't match a corona either). One of the outer rings must be the 22-degree halo, but what's the other one? It looks like the 22-deg halo repeated. Their inner edges are reddish, as it should be for the 22-deg halo.
     
  6. SR1419

    SR1419 Senior Member


    he seems to conflate sundogs and halos- whilst related they are not the same thing...when I posted that they are not particularly rare- especially in winter, he deleted my post. I also asked if he really thought aluminum refracted light :)
     
  7. Mick West

    Mick West Administrator Staff Member

    Comparing to an actual 22° halo from one of Roddie's excellent time-lapses(on the left, and a section over the top right), from the same viewpoint. The indicate ring does match a 22° halo. EDIT: This seems to be inaccurate, due to camera distortion .

    [​IMG]

    The time-lapse lens is a bit fisheye, so the buildings don't line up exactly.
     
    Last edited: Feb 25, 2016
  8. skephu

    skephu Senior Member

    Great, so the inner of the outer rings is the 22-degree halo. Then we have an extra ring. It's the "27-degree halo" or something :)
     
  9. skephu

    skephu Senior Member

    Look at what I found searching for 28-degree halos:
    Andrew J. Weinheimer and Charles A. Knight: Scheiner's Halo: Cubic Ice or Polycrystalline Hexagonal Ice?
    J. Atmos. Sci., 44, 3304–3308.
    A more recent description on an unlikely web site:
    Now if this thing has only been reported 7 times in the last 350 years, and Patrick Roddie observed it then he can really say it is incredibly rare!

    Could it really be a Scheiner's halo along with a 22-degree halo along with a corona? If yes, that's really an extraordinary phenomenon.
     
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  10. Mick West

    Mick West Administrator Staff Member

    Awesome! It looks like it is actually an additional halo, made with cubic ice! Check out the colors here.

    https://www.wunderground.com/wximage/Skyywatcher88/111
    [​IMG]
     
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  11. Mick West

    Mick West Administrator Staff Member

    I wonder if the inner small ring is actually an artifact of Scheiner's halo, an addition small inner halo that's not normally well observed unless the sun is occluded.
     
  12. Mick West

    Mick West Administrator Staff Member

  13. skephu

    skephu Senior Member

    I just found this: World Database of rare halos
    From this page it turns out that there are lots of halos:
    6, 9, 12, 18, 20, 23, 24, 28, 35-degree halos.
    Unfortunately most of the image links are dead on that page.
    So the smaller inner rings may also be halos rather than a corona.
     
  14. Mick West

    Mick West Administrator Staff Member

    More images and comments
    http://spaceweathergallery.com/indi...d=123036&PHPSESSID=nr8hai2s5q7draeqte84h2t6k6
    [​IMG]

    Last seen 1974. Now that's "incredibly rare".
     
  15. Mick West

    Mick West Administrator Staff Member

  16. skephu

    skephu Senior Member

    Of course with so many halos, it becomes harder to argue that it's all just ice crystals.
     
  17. Mick West

    Mick West Administrator Staff Member

    Well, except that this is unlikely to be seen again in the next several years. So unless chemtrails have only been sprayed on this one day, then it's all ice crystals.

    And of course these halos are explained by ice crystals, just odd shaped ones.
     
  18. skephu

    skephu Senior Member

  19. Spectrar Ghost

    Spectrar Ghost Senior Member

    This is where I really get hung up on 'chemtrails'. By choosing to ignore the science, one misses out on the truly strange and beautiful parts of meteorology.

    The real explanations of phenomena like this are so much more interesting than arguing over pylon drains and ballast barrels.
     
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  20. Mick West

    Mick West Administrator Staff Member

  21. Dan Page

    Dan Page Active Member

    This phenomena was unusual enough to make it into todays www.spaceweather.com and explained as "tiny pyramids of ice", so it looks like you all were mostly spot on, and again the chemmies are a little off the mark.
     
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  22. skephu

    skephu Senior Member

    That's a different assessment from what we arrived at. From Mick's comparison with an earlier photo by Patrick Roddie, we found that the inner outer ring is the 22° halo, and in that case the outer one must be at 28°. But if Les Cowley is right then the inner one is at 18° and the outer one should be the 22°.

    If we take into account the very faint outermost ring here:
    upload_2016-2-25_11-44-14.

    and we assume that it's at 35° then Les Cowley's assessment is right. But maybe it is the 46° halo, and then our assessment may be the correct one.

    Hard to decide with such a large choice of possible halos.
     
  23. Trailspotter

    Trailspotter Senior Member

    Is there a time stamp? I could not find the original.

    EDIT
    Found the original photo on his Facebook. It was posted at 22:54 GMT (14:54 PST).
     
    Last edited: Feb 25, 2016
  24. Pete Tar

    Pete Tar Moderator Staff Member

    Okay, I finally have to ask.
    Circles are 360 degrees, so how can there be a 22 degree circle? The definition for the sun halo says it's 22 degrees from the sun, but it surrounds the sun completely, so what does that actually mean? I get it seems to be referring to distance from the center, but don't understand how it's measured or why it's expressed as a degree.
     
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  25. skephu

    skephu Senior Member

    It's the angle between the sun and the halo.
    [​IMG]
     
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  26. Pete Tar

    Pete Tar Moderator Staff Member

    So is a rainbow half of a 180 degree halo?
     
  27. skephu

    skephu Senior Member

    No. A rainbow is at ~41 degrees from the anti-solar point, so it would be a 180-41 = 139-degree halo.
     
  28. Trailblazer

    Trailblazer Moderator Staff Member

    As @skephu says, it is a measure of the diameter (or radius, in this case). If you don't know the distance of an object (or, as in this case, it is not a physical object) then the only way you can express its size is in degrees: the amount of the field of view that it occupies.

    If there are photos of these haloes taken using a known camera and lens, then it would be possible to determine which halo is which by comparing the apparent diameter to the known field of view. (For instance, anyone with an iPhone 5 who has tried to photograph a 22-degree halo, which is 43.1 to 44.7 degrees in diameter, red to blue, will have found that you can't quite fit the whole thing in, because the field of view along the short side of the camera is only about 43.8 degrees.)
     
  29. Mick West

    Mick West Administrator Staff Member

    Rainbows are 42° you can generally only see half of it because the rest would be underground. If you get high enough you can see the whole thing.
    [​IMG]
     
  30. Trailblazer

    Trailblazer Moderator Staff Member

    A 180 degree halo would be a straight line :)

    Well, kind of. It would be a line bisecting the sky between the sun and the point opposite the sun. At sunset or sunrise it would pass directly overhead.
     
  31. Mick West

    Mick West Administrator Staff Member

    No, it would be point of light opposite the sun.
     
  32. Trailblazer

    Trailblazer Moderator Staff Member

    You are right, I was confusing diameter with radius. That would be a 90 degree halo.
     
  33. Trailspotter

    Trailspotter Senior Member

    The photo has been taken from the roof of the building listed as his address. Adding it to Google Earth also matches the Sun position, suggesting that the photo was taken shortly before it was posted on Facebook at 2:54 PM EST.
    Scheiner's Halo GE.
    Also, the resulting horizontal field of view of 83° is consistent with the inner halos being 9°, 18° etc. This is corroborated by a flickr photo, the horizontal field of which deduced from Exif is about 60°:
    24932625480_c6d1fbc6c0_o.
     
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  34. Mick West

    Mick West Administrator Staff Member

  35. Mick West

    Mick West Administrator Staff Member

    My comparison might be a bit off, the non-rectilinear lens used for the time-lapse (note the curved sides of buildings) might be distorting things more than I thought.
     
  36. CapnPegleg

    CapnPegleg Member

     
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  37. M Bornong

    M Bornong Senior Member

    [​IMG]

    http://www.atoptics.co.uk/halo/circular.htm
     
  38. Mick West

    Mick West Administrator Staff Member

    Luckily Patrick has quite a collection of photos from similar locations.

    A 22° halo
    12111940_10156679680075595_2028457170709587122_n.

    The multi-halo in a similar location, and more importantly with what seems to be the same camera/zoom. The top of the middle building is the same size in both shots. Time reported as 10:45AM

    12743971_10156672421335595_5499361487246481662_n.

    Overlaying them with no scaling shows that the 22° halo more closely matches the outer halo

    [​IMG]
     
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  39. skephu

    skephu Senior Member

    OK, so then the outer ring is not Scheiner's halo after all. That's better because Scheiner's is too rare.
     
  40. Mick West

    Mick West Administrator Staff Member

    Yes, I've removed "Scheiner's" from the thread title. It's still a very interesting and unusual halo display though.