#18 It may seem obvious, but art does not always capture the true appearance of the Moon: where it is in the sky always tells you where the Sun is.
You will never see a crescent Moon looking like an open parachute: if the crescent is on its side, the "horns" will point upwards, indicating that the Sun is"below" the Earth’s horizon. A full Moon indicates that the Sun is "behind" the Earth.
Cecilia Payne-Gaposchkin, wrote in a 1954 astronomy textbook: "It is an amusing pastime to note the impossible moons portrayed by some artists: a new moon high in the northern sky, for instance; a full moon near sunset in the west; or a crescent with horns pointed downward."
Alice in Galaxyland: 38 things you might not know about the Moon.