How interesting! By the way, this brings back thoughts how astronomy used to be done with thin glass plates, doing wide area sky surveys. The plates would be

How interesting! By the way, this brings back thoughts how astronomy used to be done with thin glass plates, doing wide area sky surveys. The plates would be placed into the plate holder, and some pressure was necessary to deform the plate to match the curvature desired. They said you knew when you'd gone to far because you'd hear the tinkle of broken glass... (they also baked the plates in hydrogen to increase their light sensitivity)