The Concrete Donut

The Concrete Donut. . , To Aid the Construction of the Mayall Telescope , Concrete donuts like this one are sometimes used to test the mounting equipment for large telescope mirrors. The "test dummy" replica must be the same diameter and the same weight as the much more expensive glass mirror. At 150 inches in diameter and approximately 15 tons, this replica matched the expected diameter and weight of the already-ordered Mayall Telescope mirror blank (the rough casting from which the mirror is made)., Mirror blanks were always made slightly bigger than the intended mirror diameter so that the uneven edge could be ground off. In the case of the Mayall 4-meter mirror, the form was 158 inches. As it turned out, the whole 158-inch diameter blank was smooth to the edge, so it was decided to make the final mirror as large as possible by using the entire diameter of 158 inches. Thus, this 150-inch concrete replica was not usable as a "test dummy"., Another test replica was constructed with a diameter of 158 inches. To provide the correct weight, the replicas are thinner and the center holes larger than the actual mirror because concrete is denser than glass. The new replica was used to successfully test the Mayall mount, and was then sent to Cerro Tololo Inter-American Observatory, in Chile, for testing the mount of the 4-meter Blanco Telescope. The previously unused 150-inch test replica has found new life as this exhibit., Scenes from Tohono O'odham Life , Tohono O'odham artist Michael Chiago shows a depiction of life on the Tohono O'odham Reservation from about 100 years ago. He took inspiration for the scene from his own childhood memories growing up on the portion of the Reservation located near Casa Grande, Arizona., On the left, petroglyphs can be seen on the dark rocks in the foreground. Included are two rams, the Sun, a snake, and maze. Sitting atop the Saguaro cactus is a hawk, while two vultures glide in the sky. Beyond is the mountain known as Ioligam Doag to the Tohono O'odham and as Kitt Peak to astronomers. Notice the telescope domes on the mountain., At center left, a man is using a long tool to remove the ripened fruit from the Saguaro. The tool is comprised of Saguaro cactus ribs wired together with crossed pieces of Greasewood near the middle and top of the tool. In the distance, a windmill pumps water to a large, white storage tank and the overflow ponds on the desert surface, providing water to two horses. In the garden, a man is picking corn and a woman harvesting chile peppers and melons., The traditional mud brick house is in center right. A ramada holds drying chile peppers. Just right of the blue door is a special pot for holding water.An outdoor oven and two pots containing bread dough is near the left corner of the house. To the right, two women are spreading out Saguaro fruit on a blanket. The white tubs hold water to clean clothing and a drying line is nearby., The open-air wagon parked near the storage building would have been pulled by two horses. The woman near lower right is carrying a basket with harvested Saguaro fruit. The fruit can be eaten directly, used to make syrup, or fermented to make ceremonial wine. Beyond the clothes drying on a line is the distinctive mountain, Baboquivari. It is the most sacred place to the Tohono O'odham, the home of the creator I'itoi, who resides in a cave at the base of the mountain., Arching above is a group engaged in a traditional friendship dance. Two women are holding rattles and a man is beating on a drum; all three are singing. The night sky features a "blue moon.", Michael was encouraged to explore his artistic skills by a caring second grade teacher. He became a self-taught artist by the end of high school. After high school, he volunteered for the US Marine Corps. He spent 3 years as an active duty Marine, serving part of his enlistment in Vietnam. Upon his return to the U.S., he used the G.I. Bill to attend Maricopa began practicing as a full-time artist in 1971. His artist signature features a woman with a basket on her head and a man holding a harvesting tool.