Apparently the one full moon is not the other. This time it was warmer, 3400K. The luxvalue was lower than the first recording in september last year. It is attractive to speculate that more haze in the atmosphere (the sky looked very bright though) caused more scattering (affects blue the most) and warming up the CCT. Or the moon was lower than last time (it was), so the light travels a longer distance through the atmosphere, again more scattering.
Whatever the reason, the CCT of moonlight seems pretty variable, but the CRI is invariably high. Let’s wait for a very high moon next time and see what the CCT does then.
I just saw that as an explanation for why this month’s full moon looks more pink — it rises only to the lowest angle above the horizon.
I’ve seen some wonderful outdoor time exposures of Yosemite waterfalls made with moonlight. They make “moonbows” too dim for the eye that cameras can capture.
So now it is half a year later because very high moons only occur in winter. It is two and a half weeks after midwinter, with full moon within half an hour of its highest point, less than 20 degrees from straight above. Is the tint significantly cooler than the low moon in summer?
It was to be expected: just like the sun, the moon tint is coolest when it is high above the horizon, lower duv too . The sky was clear but not completely haze-free so perhaps an even bit higher CCT could have been obtained.
This is most fascinating. I wish my budget would extend to a spectrometer like that.
It you look closely you will notice that there is a hare living on the moon, although in your original post he is turned upside down and it is harder to see him. But you will also see he is busy with a pestle and mortar compounding the Elixir of Immortality.
Perhaps your differing results correspond to different seasons when he is experimenting with different ingredients, and these in turn alter the spectrum of light reflected from them?
I don’t see how Mars would alter the spectrum of light reflected off the Moon, but that does make me think of another interesting possibility, what about measuring the spectra of a lunar eclipse, also known as a “blood” Moon, or a red Moon?
It is two days after midsummer, and I caught the full moon just as it rose above the rooftops opposite my balcony, must be less than 10 degrees above the horizon.
It is the lowest CCT that I measured sofar: 3170K, and the highest duv: +0.0068.
CCT = 3170K
duv = +0.0068
CRI = 96.5
R9 = 94.8
Today’s moon through my binoculars (not a great pic) :