[minhmeoke]

Additional pictures showing how the 20 ton, 200 inch (5.1 meter) diameter glass disk was transported across the country by train to Pasadena, CA, polished, and eventually trucked up to the Palomar Observatory:

Video of the pouring process: https://www.youtube.com/watch?v=KdqaC8pLixY&t=15s

Transport: https://sites.astro.caltech.edu/palomar/media/slideshows/mir...

Polishing: https://sites.astro.caltech.edu/palomar/about/telescopes/ima...

Click the slideshow and press the left/right arrows to advance the slides or go back.

It seems like the first mirror cracked, so they manufactured a second mirror in Corning, New York (taking 10 months to cool it down and anneal it after it was poured), moved it across the country to Caltech in Pasadena, then they spent 11.5 years polishing it down to 14.5 tons... wow! And finally trucked it over to its current location in the Palomar Observatory in San Diego. I can't imagine being the crane operator while loading and unloading this thing.

[Gare]

Video of recent recoating: https://www.youtube.com/watch?v=lkBgQaJVKjc

[yborg]

>It seems like the first mirror cracked

Firebrick bolted to the base of the mold to form the void spaces broke loose and floated to the top of the mirror blank.

[insane_dreamer]

> they spent 11.5 years polishing it down to 14.5 tons

wow, talk about a long-term project

[kumarvvr]

The site says that the first mirror cracked due to breaking of the mould.