The Art of the Crescent Moon
June 2013 :
I think I’ve found the answer to a long-standing pet peeve of mine.
For many years, whenever I’ve seen drawings of a crescent Moon in a night sky – especially in the daily comics – the horns of the Moon have invariably faced toward the right, like so:
. As a lover of astronomy, I shudder every time I see the poor Moon exposed in such a fashion.
The sky, from our view, seems to travel from east to west. When the Moon is visible, it also appears to move with the stars. Actually, the Moon is moving independent of the rest of the sky – travelling about 2,000 mph west to east, or counterclockwise against the stars. However, it is far enough away, about a quarter million miles, that for our swift looks, it appears to be moving with the rest of the sky.
In thinking what this has to do with the shape of the Moon: Let’s start with the Moon at “zero,” that is, when it is in the same part of the sky as the Sun. The only reason we see the Moon is because it reflects sunlight, with one half of the Moon lit at any time. When the Sun and the Moon are on the same side of the sky, the side of the Moon away from the Earth is lit, and the side facing us is dark, making a “new” Moon.
The next night, the Moon will be about 14 degrees east of the Sun, and will set just about an hour after sunset. If you could see the Moon before it leaves the sky, it would show just a little sliver of itself. And, because the Moon is located to the left of the Sun, the right side of the Moon will be lit, like so: 
.
Every night, the Moon will continue to be around 14 degrees farther to the left of the Sun, and we see more of it lit. Finally, two weeks after “new,” the Moon will be opposite the Sun, and we see its entire lit side, the “Full Moon,” rising just as the Sun sets.
The next night, the Moon will seem to start its trek toward the Sun. Each night, we will see a little less of the Moon than the day before. And, because the Moon is now to the right (west) of the Sun, the sunlit side is now the left: . Each day, the Moon will appear smaller and smaller until it is again “new,” and the process starts all over again.
Now, on to the art of the Moon. Invariably, when a person draws a crescent Moon in the nighttime sky, he will represent it like so: . For the Moon to be seen like this in the sky, the viewer would either have to be up very late (or get up just before dawn), or look up at the Moon when it is in the early daylight hours, generally before noontime. The proper crescent for a normal night sky should be this: .
But, then, why does almost everybody draw the Moon backwards? After trying to answer this question for several years, I believe I’ve found the answer – courtesy the February, 1981 Omni magazine (living proof – never throw anything away). The reason is that most artists are right-handed, and drawing the Moon that way is more comfortable for them. For myself, a left-hander, it feels more natural to draw it the other (actual) way – try it yourself.
My main reason for writing this is that artists should try for truth in art, even though something doesn’t “feel” right. Of course, sometimes it does appear there are other points that must be considered: I recently spoke with an artist who had done this reversal of the Moon for a concert series poster. Her defense – artistic license. All right, I can concede: Perhaps artistic license is a viable rationale. But, so, too, is good science.
