arc-en-ciel lunaire

CONT: Beaucoup plus rare et bien moins spectaculaire, l'arc-en-ciel lunaire est pour le reste similaire à l'arc-en-ciel solaire. C'est un arc [très peu] coloré [ordinairement blanchâtre, très peu d'auteurs disent y avoir distingué une ou deux couleurs] qui ne se présente qu'à l'observateur qui tourne le dos à la Lune [...]

CONT: A night time rainbow is sometimes called a moon bow because it is a reflection of the light of the moon. ... Any rainbow comes from light hitting drops of rain and going into the drop and being reflected off of the inside edge. As the light leaves the drop on it's return journey the other side of the drop acts like a prism and separates it into the colors of the rainbow. ... with moon light it makes something shaped like a rainbow with just a hint color. Moon bows occur in the side of the sky opposite the moon.
OBS: Even though the optics of both is the same, the luminance of the lunar rainbow is much lower. As a result of the eye's reduced sensitivity to color at low light levels, the bow may exhibit little color. There are several reasons why the lunar rainbow is seen much less frequently than the solar bow. While the moon and sun spend equal time above the horizon, when they are both present, only a solar bow can be seen. This, by itself, means that the lunar rainbow could form only half as often. Further, the moon goes through phases, and so even at night may not contribute enough light to produce a discernible bow. Finally, the convective showers in which the rainbow is frequently seen are much less common at night.