| Here is something puzzling. Last week I looked up into the clouds and was startled by an arc of a rainbow that was not concentric about the sun. In fact the sun was rather low, in the late afternoon, and the rainbow was quite high. In the image in my dropbox at this link, the location of the sun is approximately at the red X in the lower left. The sky in the direction of the sun was cloudy but the sun was very apparent (although not as apparent in the image). The rainbow persisted for at least fifteen or twenty minutes, dying down gradually but not changing position. I tried to think of what light source could produce the rainbow as I saw it. I tried to conceive a large structure sitting behind me, some distance away, that might reflect sunlight so that perhaps the rainbow could be concentric (in projection) around that. Perhaps some kind of water body, or a highly reflective building, but I couldn't think of one and anyway I didn't think that would do. But later, about an hour, when I went outside to look again, I looked way up. What I saw was a bright half moon. So here's my question: Could the moon have been bright enough to produce the rainbow I saw in the clouds above me? I think the relevant angles might have been somewhat appropriate, but I didn't check. In one hour the moon moves fifteen degrees; I should have measured the angle between the moon as I saw it and the direction to where the rainbow was . . . but I didn't. In full disclosure, I took the photo with a 5D Mii, with my lens set to 35mm, and the only post processing I did was to add the X for the sun and used Genuine Fractals to reduce the size of the image to 6 x 9 inches. Comments, please? -yoram |
