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Rainbow Colors Observed When Viewing the Moon with Binoculars

-- Elisa | October 6, 2020

Question:

Hello! I live in Massachusetts. I was using a Nikon Aculon 10 x 50 binoculars to view last night’s Harvest Moon. I saw a very thin band of rainbow colors closely surrounding the rim of the moon, with red, yellow, orange appearing on the southern edge, and green, blue and purple appearing on the northern edge. I have only been able to find information about halos around the moon on the internet, rather than about colors along the rim of the moon. I wanted to ask if this stunning, impressive phenomena had a name? Thank you so much for any information you can provide. I look forward to hear from you! Elisa

-- Elisa

Answer:

I believe what you were seeing is chromatic aberration from your binocular’s optics, which causes different wavelengths of light coming from the Moon to come to a slightly different focal point at your eye. This would cause the Moon to appear to have a colored edge, with different colors showing up at different places on the Moon’s edge.

-- Jeff Mangum

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