ELT 2nd-ary mirror!

[deanm]

"The casting of the secondary mirror blank for ESO's Extremely Large Telescope (ELT) has been completed by SCHOTT at Mainz, Germany. The completed mirror will be 4.2 metres in diameter and weigh 3.5 tonnes. It will be the largest secondary mirror ever employed on an optical telescope and also the largest convex mirror ever produced."
Dean
https://www.sciencedaily.com/releases/2017/05/170522080934.htm

[julianh72]

Interestingly, the 4.2 metre secondary mirror is significantly bigger than the segments making up the primary (they're "only" 1.4 metres across - but there are a LOT of them - 798, to be precise).
https://www.eso.org/public/teles-instr/elt/elt_num/

[julianh72]

And then of course, there's the tertiary, the quaternary and the quintary(?) mirrors - this baby uses a 5-mirror design!

[strongmanmike]

Amazing...4m was the standard primary mirror size not that long ago (70's and 80's) and while it's been 8-10m for the last 20 years or so, this scope is going to smash that standard :eyepop:...cool times ahead :thumbsup:

Mike

[sil]

How many decades of constant cloud cover would this toy attract?
:lol:

[Atmos]

22nd century :lol