Mountaintop blasted to build huge telescope

[Mr_P]

Doh live feed failed so no no big explosion on channel 4

Blowing the top off a mountain

see the story in full at 8:41 ish on 4+1

Double doh we missed it BBC live feed here and the story in full

http://www.bbc.co.uk/news/science-environment-27902611

I'm sure someone will find it on the web somewhere, if you do please post.

 

[cutting42]

A huge anticlimax, I would not bother

 

[Richard863]

Hi if you want a picture of the beast google https://www.google.co.uk/search?q=europ ... ope+(e-elt)&client=safari&rls=en&tbm=isch&tbo=u&source=univ&sa=X&ei=Tr6jU_b4JIShO46DgfAK&ved=0CFQQsAQ&biw=2333&bih=1292 plenty of them. The anticlimax similar to the football TV channels

 

[Jonzjob]

Here's the story, but no video

http://thehigherlearning.com/2014/04/21 ... r-planets/

 

[Mr_P]

Here it is :-

http://www.space.com/26305-extremely-la ... blast.html

Apologies not worth the effort of watching the annoying commercial first.

 

[Jonzjob]

No ad in front for me and that is really exciting. In fact I would place it alongside, if not in front of, watching paint dry :mrgreen: :mrgreen: :mrgreen:

 

[Mr_P]

No commercial is that down to your location in France or blocking software ?

Just need one of the astronomers on here to explain why they didn't / couldn't build this in 1990 if its going to be 16 times sharper than hubble.

 

[Jonzjob]

No commercial is that down to your location in France or blocking software ?

Absoulutely no idea

Probably not enough computing power the control all of those mirrors to build it back in the 90s. Otherwise they would probably have made on HUGE mirror even more bent than the original Hubble jobbie :mrgreen:

 

[Mr_P]

Realise my trusty Atari ST or a 286 wouldn't be upto the job but would have thought an 80's super computer could have handled it.

 

[bugbear]

No commercial is that down to your location in France or blocking software ?

Just need one of the astronomers on here to explain why they didn't / couldn't build this in 1990 if its going to be 16 times sharper than hubble.

I "suspect" 2014 technology, both optical and computer, is better than 1990 versions. :roll:

BugBear

 

[Mr_P]

Just need one of the astronomers on here to explain why they didn't / couldn't build this in 1990 if its going to be 16 times sharper than hubble.

I "suspect" 2014 technology, both optical and computer, is better than 1990 versions. :roll:

BugBear

Thanks Sherlock :roll:

but was hoping for a more detailed answer.

 

[finneyb]

Just need one of the astronomers on here to explain why they didn't / couldn't build this in 1990 if its going to be 16 times sharper than hubble.

Why couldn't E-ELT be built in the 1990's? Two technical reasons. Firstly, the mirror is almost 800 segments that operate separately from each other which needs a technique known as adaptive optics - not available in the 1990's - each segment has computer controlled actuators that adjusts the segment individually. This is needed for two reasons the self-weight of the 39m diameter mirror will cause sag in the mirror and even a very small deflection is not acceptable so let it deflect and adjust using the actuators to compensate. The second reason for the adaptive optics is that the E-ELT needs to look through the atmosphere which is variable and changes constantly. They fire a laser into the sky to create an artificial star a computer constantly monitors the E-ELT image of the artificial star and feedbacks to the actuators to focus the image and thereby compensate for the effects of the atmosphere and sag for everything in E-ELT's field of view. The actuators will be constantly adjusting.

The second technical reason why it couldn't be built in the 1990's is the grinding of the mirrors, both for accuracy (Hubble had an issue initially until they sent a repair crew up on the Shuttle) and speed of manufacture; with spares there are almost 1000 segments. They work to nanometres (a nanometre = one billionth of a metre) requiring purpose made computer controlled machines and even then they have had problems grinding the edges of the segments. http://spie.org/x93597.xml

HTH

Brian

 

[Kalimna]

I imagine that cost will also be an issue. Even if the technology was available at Hubbles' construction, it would have been considerably more expensive to implement.

Adam

 

[monkeybiter]

They fire a laser into the sky to create an artificial star a computer constantly monitors the E-ELT image of the artificial star and feedbacks to the actuators to focus the image and thereby compensate for the effects of the atmosphere and sag for everything in E-ELT's field of view.
Brian

What do they 'fire' the laser at? The image would require a reflective surface.

 

[finneyb]

They fire a laser into the sky to create an artificial star a computer constantly monitors the E-ELT image of the artificial star and feedbacks to the actuators to focus the image and thereby compensate for the effects of the atmosphere and sag for everything in E-ELT's field of view.
Brian

What do they 'fire' the laser at? The image would require a reflective surface.

They fire the laser at the top of the atmosphere when the laser light hits the sodium atoms there it is absorbed by the sodium and then re-emitted in all directions much as a star. This may help also
http://www.youtube.com/watch?v=h-fQp3uomKc

Brian

 

[Kalimna]

Fascinating stuff, Brian. I was under the impression that atmospheric dust provided the reflective surface.

Cheers,
Adam

 

[finneyb]

Adam,

I bet they wouldn't open the telescope housing if there was much atmospheric dust about - wouldn't want to get it on those mirrors - I'm not sure how they clean them, but I'm not doing it! And too much dust or turbulence in the atmosphere will prevent E-ELT, or any other telescope, getting an adequate image. While it is on top of the mountain to be above the pollution and reduce the distance it views thro the atmosphere it will have down time due to poor atmospheric conditions.

Brian

 

[Kalimna]

No, I meant the fine microscopic dust particles that are present in the atmosphere all the time, not so much that which is pollution dependent or due to meteorological disturbances.
As for cleaning, I wonder if they use a simillar mechanism to digital SLR mirrors - some vibrational cleaning?

Cheers,
Adam

 

[monkeybiter]

They fire the laser at the top of the atmosphere when the laser light hits the sodium atoms there it is absorbed by the sodium and then re-emitted in all directions much as a star. This may help also
http://www.youtube.com/watch?v=h-fQp3uomKc
Brian

Thanks. I wasn't aware of a sodium layer. Interesting vid.