Halos

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• • March 21, 2016 at 2:41 am #88640
    Marsha Smithhisler

    Participant

    Has anyone ever seen an oval halo around the moon? We had one tonight, the first I or my husband have ever seen. The edge was thick, like a smoke ring, and brightly lit to an almost pink color. Don’t know how long it lasted, as we just discovered it while putting the dog out one more time for the night. It lasted around 5 minutes or more after that, and I tried to get a picture, but my phone doesn’t take great pics even in daylight. It’s gone now, and the sky is as clear as can be. I googled oval halos and found some articles that refer to them as circumscribed halos. However, the articles referred to such halos as surrounding the sun. Any information would be appreciated. Thanks!

  • March 21, 2016 at 8:45 am #88641
    Gavin Pretor-Pinney

    Keymaster

    Hi, Marsha. What you saw is known as a ‘lunar halo’. This forms when the moonlight is refracted, and so bent, as it shines through the minuscule ice crystals of a high cloud like Cirrostratus. The crystals have to be shaped like tiny hexagonal columns or plates which act like tiny prisms. The optics are the same as a ’22-degree halo’ around the sun. But because moonlight is so much dimmer than sunlight, it can be difficult to see the colours of a lunar halo, and it is a hard optical effect to photograph. Here are some images of lunar halos on the Society gallery:
    https://cloudappreciationsociety.org/gallery/photo-n-3719/
    https://cloudappreciationsociety.org/gallery/photo-n-2849/
    https://cloudappreciationsociety.org/gallery/photo-n-2578/

    Also, I discussed the effect (and mentioned the lunar version) in a chat with the Weather Channel recently:
    

  • March 21, 2016 at 11:44 pm #88661
    Howard Brown

    Participant

    Marsha, Gavin did not mention the oval

    http://www.atoptics.co.uk/fz409.htm

  • March 22, 2016 at 11:55 am #88668
    Marsha Smithhisler

    Participant

    Thank you both for the information. We’ve seen halos around the moon many times, but this is the first oval (I suppose elliptical would be a more scientific word) that we had ever seen. Maybe it is a once-in-a-lifetime event. We couldn’t get any good pictures, but the ones in the link that you sent, hygge, were very similar. Thanks.

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