UA spinning mammoth mirror for Chilean telescope
The UA's acclaimed Steward Observatory Mirror Lab fired up its furnaces yesterday to begin casting a 211/2-foot-wide mirror - the second one for Chile's Magellan telescope project.
The $72 million project will add two telescopes, Magellan 1 and 2, to the Las Campanas Observatory on Manqui Peak, Chile. The Carnegie Institution of Washington in conjunction with the University of Arizona, Harvard University, the University of Michigan and the Massachusetts Institute of Technology are working on the project.
A 180-foot tunnel will eventually link the scopes and combine their light to produce ultra-fine images.
"Sharpness (of the images) depends on the diameter of your telescope," said UA astronomer John Hill, who directs castings at the mirror lab. "By combining both telescopes, your sharpness increases."
UA's successful casting of the first 211/2-foot-diameter reflector six years ago was hailed as the most significant large telescope mirror-making breakthrough in the last 50 years.
That mirror was made as a replacement for the Multiple Mirror Telescope on Mount Hopkins, south of Tucson. Polishing and testing was completed last spring for the mirror, which was transported to the mountain in July.
Since them, the mirror-making process has become faster and more streamlined, Hill said.
"I'm not ready to say that this is routine and boring yet," he said. "It's still fun to do."
The Magellan 1 mirror, the second 211/2-footer cast by the UA's mirror lab, came out of the oven in 1994 and is now in the lab beneath Arizona Stadium. The mirror, which is being polished by a computer-controlled device, should be completed in about two months.
Magellan 1 will be shipped from Tucson to South America next summer. It is expected to see its first light sometime in late 1999.
The mirror team Friday loaded 22,750 pounds of glass into a pre-fabricated mold, beginning the casting process. The furnace will gradually heat up until Monday, when the glass will be hot enough to melt.
Once the glass begins melting, the mirror makers will spin the furnace at 7.5 revolutions per minute, using centrifugal force to mold the molten glass into a parabolic shape, Hill said. If all goes as planned, the glass will reach a peak temperature of 2,156 degrees Fahrenheit Tuesday morning.
The molten glass will spin for two or three days before it starts to slowly cool, Hill said. The cooling process is expected to last until the end of November.
Magellan 2, however, is not finished when it gets out of the fire. It still must be polished and tested, Hill said.
The Magellan telescope should be operational in 2002.
Michael Lafleur can be reached via e-mail at Michael.Lafleur@wildcat.arizona.edu.