‘Technicians on Saturday are set to cast 20 tons of glass for the third of seven ultra-precise primary mirrors that will make up the 72-foot Giant Magellan Telescope, scheduled for completion in northern Chile’s arid Atacama Desert in 2020.
The parabolic mirror will be cast at the University of Arizona. The molten borosilicate, made by the Ohara Corporation, will be spun cast at 2140 degrees Fahrenheit.
Describing the production of the first such mirror in 2005, the Lab explained the process:
The glass was “… melted in a rotating furnace until it flowed into a honeycomb mold. Once the glass had cooled and the mold material was removed, scientists at the lab used a series of fine abrasives to polish the mirror, checking its figure regularly using a number of precision optical tests.”
How precise?
Once the mirror cools, and the polishing complete — a process that is expected to take a year — it will be accurate to within 1/20 the wavelength of light, or put another way, “one part in 10 billion in terms of precision manufacturing,” according to Patrick McCarthy, the project’s director.
When finished, the telescope — which includes another seven smaller mirrors to direct the collected light to a focal plane — will employ adaptive optics to compensate for atmospheric disturbances that might otherwise blur the image. The GMT is expected to offer 10 times the resolution as the Hubble Space Telescope…’
CrusaderRabbit
FOR LIBERTY
This will probably be the last large frame terrestrial telescope built.The next order or resolution with require the mirror and electronics be chilled close to absolute zero to reduce molecular vibration in the mirror substrate.The James Webb Telescope should achieve that,IF it is finally completed and launched in 2018.
The next step in building the Large Magellen is coating the mirrors.Here is a video of the process on a 200″ Mt Palomar mirror-
http://youtu.be/gxp6aMhoT9U
Very cool link–and I ended up watching how to make a solar cooker out of a junked TV fresnel lens, somehow.
Heh!
I was wondering what to do with 25lbs of Mercury,then I found this-
http://youtu.be/Q5Cr9P-Q88Y
Off to find an old washing machine,be back later
Errr..you’re going to need some way to control the speed of rotation veryveryveryvery accurately!
Oh yea of little faith.
No problem,found some slightly used sash cord for a drive belt and a cake mixer for the variable speed.And to think people had doubts about my Hybred car
http://youtu.be/HxYe26CIvuY
Darin- I learn something every time you comment – thank you for all of the links –C-CS
Thank you Carol,and to think just three decades ago I was the guy in class who kept throwing things at the teach and cussing.Now here I am about to gradjamate highersckool
U can spel injunere and everything now.
ROF LOL si-eye kin spel tu–
C-CS
“one part in 10 billion in terms of precision manufacturing,”
So? any husband will tell you that his wife can detect finer errors in making the bed
Ain’t THAT the truth, Michael.
Especially when he makes it
Well, of course–commenting when SWMBO makes it is to invite the charge of “pedant”.