I also have astigmatism in my left eye, and while I too will occasionally see multiple copies of the moon, that extends to anything that's bright against a dark background, like streetlights and projected screens. In fact there is one moon, and the appearance of multiple copies of these things is due to the way light is being reflected on the surface of our eyes. The reason that corrective lenses fix this (to an extent, at least in my case even with glasses on there isn't perfect clarity) is because they are shaped to accommodate the deficiency inherent in your eye.