OPOD - Stacked Blue Moons

Stacked 'Blue' Moons

At least three stacked "Blue Moons" rising and descending over the Rio de la Plata, Argentina on 31st August '12. Images by Luis Argerich.

In the large image we see Mare Crisium near the upper limb and Mare Tranquillitatis draped over the lip of the uppermost domed mirage. The Moon's shape constantly changed as its rays differently traversed the many temperatured atmospheric layers.

Images ©Luis Argerich

Blue Moons:

Real blue moons are exceeding rare - "as rare as a blue moon". They occur when moonlight is filtered by smoke and droplets from forest fires, volcanic ash and other particles. When the particles are in a special size range of .5 - 2 micron (Mie scatterers) they can sometimes (but rarely) selectively scatter long wavelengths to leave the moon and sun a blue or indigo colour.

Then there are the purely calendrical blue moons when there are two quite ordinary full moons in a calendar month.

Stacked Moons:

Stacked or pancake moons and suns are miraged images - miraged slices of the lunar or solar disk.

Temperature inversion layers - a kinked vertical temperature profile where abnormally warmer air overlays cooler.

Moon rays are refracted and deflected as they pass between the layers of different temperature. In the simplest and purest case of a single inversion layer there can be three image slices. Two slices are erect and rise at moonrise. The third image slice is inverted and descends.

Luis's mirage is more complicated - They usually are!