On Saturday, January 14th the Mirror Lab will be casting the second of seven 8.4 meter mirrors for the Giant Magellan Telescope. See the press release for the event here.
They have placed 21 tons of borosilicate glass into a mold that is sitting within a giant rotating oven. As the temperature increases, the glass will melt, and the rotation will evenly spread the molten glass over the mirror's honeycomb skeleton.
The Mirror Lab has set up live webcams inside the oven, will relay oven temperature and rotation speeds telemetry for the mirror casting. You will be able to watch the event as it unfolds here:
Times have changed and the methods of casting telescope mirrors has too. Here's how Corning Glass Works cast the mirror for the 200-inch telescope back in 1934:
Times have changed.