"It's an interesting experiment to see how close to the time of the full moon you can notice that it is not full."<br /><br />I tried this with a telescope. I did it on a night when the Moon was heading for eclipse. Several hours before the Moon touched the penumbra of Earth's shadow, the shadows on its surface became less noticable. But after a point, they refused to get any smaller, Rather, they rotated from the Moon's west limb, to its southern limb. I observed until about 1 hour prior to penumbral contact, and was convinced that even if I watched until umbral contact, that I would still see some shadows on the Moon's southern limb.<br /><br />Ever since then, I've been convinced that it is not possible to see a completely full moon from Earth. I take the term "full" to mean "fully illuminated", ie, no shadows visible on the surface of the Moon, either from its own releif, or the Earth' shadow. <br /><br />But with the naked eye, the Moon was indistinguishable from full for the entire evening.