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Ring of light

  1. Mar 23, 2010 #1
    I was in the French Alps the other day, high in the mountains (not sure if this is relevant), and, on the night of a full moon, with mist in the sky, there was a circular ring of light around the moon.

    The ring subtended an angle about 5 times that subtended by the moon (that is to say, it looked about 5 times as wide as the moon), and, the colours were split up (though not as well as in, say a rainbow - they sort of merged together a bit).

    The inside colour was (I think - may have forgotten) red.

    Rainbows appear on the 'other side' of the sun, due to the geometry of the spherical raindrop, so it certainly wasn't a standard rainbow. Also, it subtended far too small an angle (I could easily see the whole ring, with the moon at the centre)

    Any ideas what was happening?
     
  2. jcsd
  3. Mar 23, 2010 #2
  4. Mar 23, 2010 #3
    Thanks, that's pretty interesting.
     
  5. Mar 23, 2010 #4
    Your welcome, I would ocassionally see sun dogs in Colorado Springs.
     
  6. Mar 23, 2010 #5
    Sounds like you were observing a ring of colors analogous to a rainbow..
    try here
    http://en.wikipedia.org/wiki/Atmospheric_refraction

    and also note optical dispersion....

    basically, different colors are refracted (bent) at slightly different amounts so the colors get separated and spread out...like a prism disperses sunlight...the degree of bending is dependent on atmosphere conditions like density, humidity, particles in the air,etc.
     
  7. Mar 23, 2010 #6
    Naty1 - I'm not sure this accounts for the ring. Look at http://en.wikipedia.org/wiki/Sun_dog , posted by jmatejka. That seems to match up perfectly with what I saw. The similarities of the visual description I gave to the one in the article is actually quite uncanny.
     
  8. Jun 29, 2010 #7

    Evo

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    Staff: Mentor

    It's a halo. More specifically, yours sounds like a corona.

    http://home.hiwaay.net/~krcool/Astro/moon/moonring/

    I witnessed a very rare event where the halo started out as a very small ring right around the moon then continually grew bigger until it filled the sky. It made the news. Supposedly the rings do not move.

    http://curious.astro.cornell.edu/question.php?number=79 [Broken]

    I also witnessed an incredible hot pink sun pillar. I have never seen a pillar of the size or intensity of the one I saw, and of course not a single camera had a working battery. First and last one I've ever witnessed.
     
    Last edited by a moderator: May 4, 2017
  9. Jun 30, 2010 #8
    It might be a 22 degree halo. These rely on ice particles in the air, so it makes sense that you would see it in the alps.

    http://en.wikipedia.org/wiki/22_degree_halo" [Broken]
     
    Last edited by a moderator: May 4, 2017
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