The changing face of the moon has long been documented by artists. In the early 1600s, the introduction of the telescope allowed for detailed sketching of lunar features at the eyepiece. The most celebrated early telescope sketcher was Galileo Galilei. His artistic training allowed him to understand that the jagged appearance of the lunar terminator (day/night line) seen in the eyepiece was due to the topography of craters, mountain, and ridges on the moon. These irregular shadows on the moon had puzzled earlier observers that considered the moon to be a flat disk with markings on it.