This info from "The Birth of a New Physics", by Bernard Cohen, pg 24. Here is Aristotle:
"The rainbow is seen by day, and it was formerly thought that it never appeared by night as a moon rainbow. This opinion was due to the rarity of the occurrence; it was not observed, for, though it does happen, it does so rarely. The reason is that the colours are not easy to see in the dark, and that many other conditions must coincide, and all that in a single day in the month. For if there is to be a moon rainbow it must be at full moon, and then as the moon is either rising or setting. So we have met with only two instances of a moon rainbow in more than 50 years."
The full moon is this Saturday. Let's all look.