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A circumscribed halo is a type of halo, an optical phenomenon that circumscribes a related phenomenon, the 22° halo centred on the sun. When observed, a circumscribed halo is normally oval in shape and, at the points directly below and above the sun, lies tangential to the 22° halo. It forms when, as the sun rises, the upper tangent and lower tangent arcs extend into each other and close in on the 22° halo.〔 (includes a composite image of a circumscribed halo)〕 As the sun rises above 70° it essentially covers the 22° halo.〔 (includes a fisheye photo of the phenomenon)〕 A circumscribed halo is more intense in colour than the 22° halo. Like many other halos, it is reddish on the inner edge, facing the sun, and bluish on the outer edge. 〔 == References == 〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「circumscribed halo」の詳細全文を読む スポンサード リンク
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