Star field

A certain shape covered with black corrundum and white corundum cross over the ground. From one end to another, there is an uneven gradient of corrumdum from black to white, and black again. There are always some corumdum particles shine by their reflection of light.

The form of the shape comes from the constellation right over the antipode of the location of the exposition. That means, the skyfield right on the head of the people, on the other side of the earth.