Moon Halo 月暈

Moon Halo

Have you ever seen a halo around the Moon? So unbelievable, I saw a huge one from the pickup truck on Bohol island (Do not know where it is? It is in Philippines.) heading northwards on 1/8/2006. I was so thrilled by what I saw all night.

This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo.

月暈

你曾看過帶有暈輪的月亮嗎？很難以相信 1/8/2006 我坐卡車在薄荷島上（這麼可愛的島名沒聽過嗎？就在菲律賓）朝北行進時 就看見了一個巨大光環的月暈 整個晚上被懾人的天象所震撼

當高空被稀薄的雲氣所覆蓋時，如果雲氣中含有數以百萬計的細小冰晶，就常會產生這種景觀。因為大部份的冰晶是呈長形的六方體，而每一顆小冰晶就像是個微小的透鏡，當光從其中的一個面進入冰晶，再從相對的面射出時，會偏折22度角，也造成月暈和月亮中心的張角恰好是22度。