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selvaarchi
2017-Nov-10, 03:38 PM
The 5th mirror for the Giant Magellan Telescope (GMT) was cast last week (2 more to be cast for a total of 7). So slow but study progress is being made. 1st light is now to be 2023 instead of 2020.

http://www.planetary.org/blogs/jason-davis/2017/20171110-gmt-update-awesome.html


As someone who writes about space, I am often asked by friends, family and occasionally media representatives to rattle off a list of exciting future space things. If given time to think about it, I usually settle on something tied to the search for life beyond Earth. Whether it's the discovery of microbes in Europa's subsurface ocean or signs of photosynthesis on an exoplanet, I hope I live to see the day when we figure out we're not alone in the universe.

Since 2013, I've been following the construction of the Giant Magellan Telescope, or GMT. The GMT is a next-generation astronomical observatory that will be built in Chile's Atacama Desert. It will have seven, 8.4-meter mirrors, giving it an effective diameter of 24.5 meters in total. For comparison, Hawaii's twin Keck Observatory telescopes have 10-meter-wide mirrors, and they are already dubbed the most scientifically productive optical telescopes in the world.

George
2017-Nov-16, 07:07 PM
They seem to be doing well. This project is not fully funded so they are progressing at the speed of funds, more or less.

selvaarchi
2018-Feb-17, 08:59 AM
More details on the Giant Magellan Telescope (GMT)and how the lenses are being cast.

https://www.popularmechanics.com/space/telescopes/a13978782/giant-magellan-telescope-chile-atacama/


The glass is made in Japan. Although the final product will look toward the future, the first steps call on glassmaking techniques of centuries past.

Craftsmen fill large handmade clay pots with one and a half tons of silica and boron oxide powders. The sandy mix goes into a great furnace, where it is heated for more than two days at temperatures as high as 1,500 degrees Celsius (2,732 Fahrenheit), melting the raw material until the 800-liter pots are brimming with molten glass. Over the course of 13 days, the material cools as the crystal-clear glass hardens uniformly, forming a structure that is resistant to heat and pressure.

The clay pots are then shattered with a sledgehammer, revealing the transparent monoliths within. Each slab weighs about a ton. The Ohara E6 glass is perhaps the purest optical glass in the world, known for its resistance to thermal expansion.

selden
2018-Feb-17, 04:49 PM
A quibble, although it's not a quibble to those involved in the project: they aren't casting glass for lenses. Those chunks of glass subsequently get melted down to form the telescope's mirrors. A picture and description of the process is available at https://www.gmto.org/2017/12/december-2017/#5th-mirror-casting

selvaarchi
2018-Feb-18, 01:05 AM
A quibble, although it's not a quibble to those involved in the project: they aren't casting glass for lenses. Those chunks of glass subsequently get melted down to form the telescope's mirrors. A picture and description of the process is available at https://www.gmto.org/2017/12/december-2017/#5th-mirror-casting

Thanks, I stand corrected.