Mohawk Valley Astronomical Society

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The Three-Horned Crescent Moon

by Perry Pezzolanella

There are countless paintings of nighttime and twilight scenes showing the Moon in various phases. If it is fully dark, the painter takes great care in using the proper phase for the time of night, and if it is less than full phase, consideration is also given in the orientation of the phase. Nothing is more annoying than having a beautiful sunset or sunrise painting, perhaps done from memory, showing the horns of the crescent Moon pointed the wrong way. In the several drawings I made during my childhood years I always had to have a crescent Moon in the sky, especially if it was spooky Halloween scenery. I took care to orient all three horns of the crescent in the correct direction. Three horns?

The Moon appears flat when shining in the sky, especially when full. The eyes have difficulty perceiving it as a 3-D globe because it is so bright against the black sky. This would give the impression that the surface of the Moon is quite smooth, but it only takes a quick look to realize that the Moon is a rugged world of mountains, craters, and valleys when observing it during any other phase besides full. The crescent phase is especially good for viewing the ruggedness of the lunar surface as this phase is not overwhelmingly bright and therefore makes it easier to see finer detail. Observing the terminator, the day-night line, as it arcs across the crescent, really gives a sense on how rugged the Moon is. The low angle of the Sun along the terminator causes the mountains and other landforms to cast long shadows. High peaks poke up into the sunlight from the darkness of night below. This gives the Moon a 3-D effect, and while binoculars and telescopes aid greatly in seeing the detail, unaided eyes can often see certain landforms easily along the terminator if they are large enough and the lighting angle is just right. The crescent’s outer rim will look smooth along with the two horns, or cusps, giving it a sharp appearance, and most of the time the terminator will appear smooth with just some jaggedness, but nothing too extreme.

Observing the 5-day old waxing crescent Moon can be exceptionally interesting if the timing and lighting both fall in place. There is a clustering of mountains to the lower left of the Sea of Tranquility that catch the rays of the rising Sun early enough that the peaks become illuminated well before the base and plains below. Theophilus, Cyrillus, and Catharina are an imposing trio of craters with rims so high and towering central peaks that are so close together that they create a bright spike in the curvature of the terminator during lunar sunrise which briefly gives it a third horn. The mountains on the rim of Theophilus tower 2.7 miles from the crater floor and catch the rays of the rising Sun soon enough and lasts long enough that a careful observer will be able to catch the third horn along the terminator, almost like a side profile of a person with a pointy nose. The Moon goes through monthly librations causing it to nod at extremes from up and down and side by side. If the libration is just right with just the correct light on the mountain peaks, the third horn will be nearly halfway along the curving terminator.

The three-horned crescent Moon in my drawings of long ago may have seemed odd and maybe just a fantasy but given the critical observations of everything around me even at that young age, there had to be some basis. Some fun research finally proved that it is a real phenomenon and there actually are enough cartoons with side profile of a face with the nose in just the correct position for a third horn. Three-horned comical (and serious) crescent faces can be found in cartoons, on dishware, jewelry, the old Pleasure Island logo at Disney World, and even inside the Barton-Brown Observatory! Is it logical to paint such a crescent in scenery? Unless it is a cartoon, probably not, but if the artist has a critical eye for detail in creating a painting showing lunar features that truly can be discerned with the unaided eye, then yes indeed, for that is what it really looks like, although not as extreme as the cartoons, or my simple drawings. Such a crescent would add a sense of eeriness to a spooky Halloween scene!