Besides the $22^ ext{o}$ halo, what other, larger halo is sometimes produced by moonlight interacting with ice crystals?
Answer
The $46^ ext{o}$ halo
While the $22^ ext{o}$ halo is the defining signature of moonlight interacting with hexagonal ice, the text notes that other, rarer rings can exist. One such phenomenon is the $46^ ext{o}$ halo. This larger circle requires a different refractive pathway: the moonlight must pass through the ends of the hexagonal prisms rather than through the side faces. Due to this requirement and the greater angular distance from the light source, the $46^ ext{o}$ halo is often too faint to be easily distinguished against the general background sky brightness when the Moon is the light source.
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Related Questions
What optical phenomenon causes the luminous ring known as a lunar halo?What precise minimum angle reflects light refraction by common hexagonal ice crystals in a lunar halo?Which specific types of high-level clouds produce the ice crystals necessary for a lunar halo?Approximately how many times the Moon's diameter must be stacked to span the $22^ ext{o}$ circle outward to the ring?What inherent geometric property of ice dictates the $22^ ext{o}$ minimum deviation angle for the halo?In mid-latitude areas, what weather condition often follows the appearance of a high-level lunar halo?For the $22^ ext{o}$ halo to form, what specific angle must the exit face be relative to the entry face of the hexagonal ice crystal?What observation suggests turbulence within the high cloud layer when viewing a lunar halo?Besides the $22^ ext{o}$ halo, what other, larger halo is sometimes produced by moonlight interacting with ice crystals?What angular span, measured by a fully stretched hand at arm's length, can help an observer estimate the $22^ ext{o}$ halo?