Re-coating a VERY LARGE telescope mirror
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- čas přidán 13. 01. 2016
- How are the four 8.2m mirrors at the Very Large Telescope moved and re-coated with aluminium?
More form the VLT: bit.ly/VLT_Playlist
Filmed at the European Southern Observatory's site at Paranal, Chile.
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and The University of Sheffield.
Video by Brady Haran - Věda a technologie
"this is not the most amazing looking building... this is just a tribute."
Wargargble couldn't remember the greatest building in the world... NAW this is a tri-eee-bute oooh
+and then i said Shoooow me the best poooolished mirror in the world, or I'll scratch your lenses.
Brilliant
The toy story sound effect was a nice touch, Brady :)
Fascinating Brady. You never think about the maintenance aspect of these very large telescopes. Thanks.
To my surprise, I actually found this to be a lot more amazing than I anticipated.
I think what really did it for me was the fact that massive yellow thing is a hovercraft, and on top of that, how much time is spent carefully maneuvering this equipment. It really drives home an understanding of just how delicate and valuable a piece of technology like this is.
My mother in law goes through the same process to put her makeup on.
+culwin
She gets carted into her own building on a 24-wheeler trailer?
+superdau well, they used a 16-wheeler before but the suspension got completely shot after just 2 trips
culwin I loled
Brady! Can we perhaps get some behind the scene stuff? I mean how often do you travel to different locations, how do you get in contact with all these people you interview and how do they respond when you ask? Do they gladly accept? How's the finance, does youtube give you all you need for all videos on all of your channels? Rarely find any video of yours that I don't like and I'm just curious how you pull it off. I'm sure many others are as well!
That's bloody brilliant! Thank you Brady!
Side note: A friend who used to be on the engineering team for the WHT told me that once while they were bringing the main 4.2m mirror back into the observatory after recoating a worker (against all rules about safe working) managed to drop a cup of coffee from a gantry down towards the exposed mirror. Luckily the cup & content went directly through the ~1m central hole & smashed onto the floor in a big puddle.
thats why they put a hole in the primary mirror!
Yes Brady, you're back!
Brady exceptional videography! Thank you!
Great vid. I had no idea they had to remake that surface every now and then. Thank you Brady.
awesome vid Brady. thanks for sharing the knowledge!
Thank you for the insight, Brady :)
Fantastic. I didn't know about that. And somehow I thought the VLT main telescopes had a segmented mirror, so I'm somewhat surprised to see that it's a single piece, and yet real-time adjustable. Thanks a lot.
your videos are fascinating, keep it up and don't waste more time on the other channels you manage :D MORE DEEP SKY VIDEOS
That's awesome! Cheers from Chile!
WOW !!!
This is so fascinating.
I so wish I could be with our homeschooled Grandchildren overseas (Thailand) and take them through your videos.
Thank you for sharing this with us, I was missing you. :)
Now Brady just needs to head to the Mauna Kea observatory...more telescope tours!
love it!
finally deepsky video
It's amazing to think that people actually made all of this!!
Ay mate, bloody good video you got here
The claw! Classic!
cool stuff
THE CLAWWWW
+Will Davis. I wonder how many viewers got that? XD
+Kris Arruda I thought it was just someone nearby making a weird noise until I read the comments.
+Will Davis. We are eternally grateful!
I saw one little smudge on the far right of the mirror, at 4:14
4:12 azimuth: 1 o'clclock radial distance ~30%
Whoo! Expensive equipment!
Thats insane
Damn Brady this was awesome. I just... I just wanna put my finger on that surface... No really that's some reflecting stuff right there. Really cool when they backed it out again.
Cant wait for a video on the recent observed gravitational waves
Neat
There was an episode of the World's Toughest Fixes where he got to see the whole process.
wow soo shinny! it would so neat to stand right next to it!.
Wow
2:42 Look at the greasy nose and forehead prints of everyone watching the mirror get re-coated lol.
Very cool! :-)
And all that so those galaxies can see themselves and see how pretty they are.
The "washing machine" so clean because the staff, being academics, take their laundry home over Thanksgiving break.
What is the degradation in quality of the optics over 18 months, are the last 3 months a bit rubbish before the reconditioning?
They probably account for sustained quality and information degradation in the service maintenance schedule. Durr.
cool!
You have great taste in profile pictures
+ᵏᵃᵃᶻᶦ :)
Can you make video about the star KIC8462852 which made to the news recently due to its (so far) unexplained changes in brightness? There is a lot of pop media articles and speculations about possible alien mega structure surrounding it. It would be interesting to hear what scientists on your channel have to say..
Brady, can you make a video on KIC 8462852?
Brady, quick question.
Are the mirrors heated? How do you account for thermal expansion?
I just imagined one of the stripping jet screws go off and fall onto the mirror, being shoved around by the other jets...
Wow! The cost of funding a telescope just gets bigger in one's mind, when the support infrastructure - a complete aluminisation facility onsite - is factored in.
At 4:08 what are those 2 small specs/circles at the bottom left side? Wouldn't they need to reclean and coat it due to those?
Ssoo. The old aluminium coating is worn down by starlight hitting it?
How do they certify the propar curvature aftar the new aluminium coating is applied?
so what do they use the machinery and factory and workers the rest of the yearfor? I cant imagine hauling other mirrors from far away but then again its all probably really expensive to maintain.
MB Actros!
So, this is a kind of a PVD coating to replace a mirror?
No shaking or vibrating because it is so fragile... even though it was just pulled down the road on a trailer...
+apburner1 That's the exact same thought I had. Nothing changes, but it suddenly becomes more fragile when it's within 50 feet of the building? :)
This must be pretty typical for larger observatories to have mirror maintenance onsite? If there was room at the top of the mountain, could they just build the MMB there and skip the road trip? Maybe it puts off too much heat and disturbs the local atmosphere?
Didn't they cover this on a whole episode of "World's toughest fixes"?
THE CLAW
the money shot at 4:03
*hnnngh*
Question: Do they resurface all four mirrors at the same time, one after the other? Or do they do one every 3 months?
That room that has to be super super clean has a pretty dirty window if you ask me.
+Fiyaaah Maybe it's dirty only on the outside, but the inside is not.
Or maybe they're just concerned about dust and don't care about water spots, because that's what it looks like.
+Fiyaaah Which is exactly why it has the window. Imagine if all of that grime on the outside of the window got into the room?
His side of the window isnt clean but the inside is
Why do they only use about 20g of Aluminum. Does the layer have to be very thin for a reason? Edit. OK I have thought about it. I guess variations in mirror thickness as the Aluminum was laid down, which might result from using too much Aluminum, would ruin the optics. IS that right?
Woot i just gave the 100th like. Thats 100 likes and zero dislikes. Good times people. Good times indeed
Brady ... why don't You link us the video with explanation of te hole in the middle? :D
+zamaszysty He wants you to watch all his videos until you find it.
+zamaszysty I think it is in most of the videos in the VLT playlist I linked to.... :) It is the whole the light sometimes passes through after it has hit the secondary mirror.
+zamaszysty en.wikipedia.org/wiki/Cassegrain_reflector
+Zack Klassen By your definition, everything you have ever learned has been spoon-fed to you, and you're guilty of your own accusation. Why you would take it upon yourself to waste your own time in order to shame someone for attempting to learn and help teach others is so beyond my comprehension that I'm going to just stop thinking about it.
it's linked at the end, isn't it?
When they are pulling the mirror back out after refinishing around 4:13 you can see several physical defects along with countless optical aberrations. Not exactly sure how they see anything with such a marred surface.
No polishing required after the vapor deposition (or whatever it was)? Straight back to the telescope building?
+Jesper Andersson given the amount they vaporize, the coating is probably something like 60 atoms thick, I don't think you can get better results after polishing
+Jesper Andersson Thickness of Al-coating is less than 150 nanometers (about half of thousand atomic layers). And in addition if process of deposition goes all right then coating has very uniform thikness (even at atomic scale) and such smooth surface like a calm liquid has. No yet way to get better mirror surface.
The sputtering of AL inside the vacuum chamber may take 45 minutes but bringing down the atmospheric pressure and getting rid of the oxigen in such a large vessel surely takes more than 45 minutes... the whole process sure lakes hours...
I saw "VERY LARGE" in the title and click on the video very excitedly because I thought you were at the Very Large Array. To bad, I would have asked if you were still in New Mexico and if I could buy you a beer.
I don't know "what sizes we are talking about" i need a banana for scale :P
I wonder why they don't use stainless steel? Maybe it still gets scratched up and is harder to re-coat
How is this done on the Hubble space telescope?
It isn't, no weather damaging that coating. Maybe a micro meteorite or two though.
why do they do this so often? every 18 months sounds quite excessive.
is the dust that bad up there? how much image degradation is acceptable?
or do they treat one out of the four mirrors every 18 months, so every mirror is really in operation for 6 years?
as you said, breaking a mirror or messing it up somehow would be very expensive, but that's only part of the problem. getting a replacement made, tested, shipped and installed would likely take years.
If it takes 6 weeks to re-coat (take down, drive it over, re-coat and put back) a mirror, does this means the VLT isn't at full strength for about 3months a year?
that toy Story reference
Is it something like a PVD coating? And why Al instead of Ag? edit: forget about the last part, the mirror is front surface.
+2dividedby3 aluminum doesn't corrode as quickly as silver, and it has a better light reflection profile.
+2dividedby3 Aluminum also has better reflection in the UV than silver for almost as high reflectivity.
Thanks to all for the responses!!!
+2dividedby3 If you google it, some recent large telescopes (but not the largest) have chosen to use silver, but it is unusual. The choice has to do with what wavelengths in the spectra they are interested in. The main information large telescopes obtain is from the spectra.
I believe silver does result in more collected light, but not necessarily in the most valued wavelengths, depending on what you have chosen to measure. Somebody already mentioned that they do treat the surface of aluminized mirrors, for various purposes, and they will also treat the silvered mirrors. I believe the mirror will also have to be recoated more often.
Aluminum does oxidize instantaneously in the air, like all metals, but aluminum oxide crystals are very transparent. However you don't necessarily want random aluminum oxide crystals all over your perfect mirror, so they "treat" the surface.
Why aluminium and not silver?
I saw a spec of dirt on the mirror in the last shot :))
+Vida András 4:15 , under the exit sign reflection
So..... More then 7 years bad luck?
How much is a fortune? I'm genuinely curious how much a replacement mirror could cost
+simontay1984 Consider that with a mirror that size, you'd likely need to build a facility capable of making and testing the mirror. Cost could easily be in the millions or tens of millions. Moreover, casting process requires very slow cooling to prevent the mirror from warping, so the total fabrication and testing process would likely take a few years.
How about making a Biophile channel for biology?
its so shiny
"I must murder it" - a cat, probably
+Azivegu - and preciouss
why isnt the mmb on top of the mountain?
+Timothy Ma Because they don't want to do the hard working stuff on that altitude - to less oxygen fro humans and machines.
Why aluminium coating? One would think aluminium oxidize rather fast.
I have a question. Why does it need to be recoated? If I'd buy a telescope myself (much smaller than this of course), would I need to recoat it as well every year and half? I'm guessing no, but then why does this one have to be?
+MaxArceus There will come a time when any mirror will need to be re-coated. But, I've had my 12 inch Meade for over twenty years and have had it re-coated only two times. I clean it about once a year, and sometimes all that is required is blowing off the dust. Moderate dust really doesn't make that much of a difference.
+Magister Ludi 2105 12 inch, nice.
Anyway, how does an consumer recoat a mirror? Bring it to the store? Does it cost much?
+MaxArceus yes. A google search or your local telescope shop should get you to the right place. A few hundred dollars or less. Obviously this depends on the size of your mirror and type etc. As shown, these scopes are open to the elements for a considerable amount of time.
Your consumer scope will see much less exposure and frankly can take quite some degredation before you will notice any difference or before it needs to be recoated. As you said, you didnt notice much difference with all the duest.
Keep your cleaning schedule up and it will considerably lengthen your scopes life.
Basically, don't worry about it.
+DENMONKEY Well, I don't have a telescope, yet. But thanks for the explanation!
no probs mate. MaxArceus
How many years of bad luck for breaking one of those?
Me with my 100 years 76mm
Why aluminium? Why not another less reactive metal so that it does not need to be replaced that often?
+Shagas Heizenberg
Did it take 4 years to make a mirror and they don't a spare? What????
I did not understand your comment
+Shagas Heizenberg My point is a larger one...not only did they picked aluminum they picked something that takes four years to make????? and the downtime on the mirror is 2 months every year because they have pull them off to work on them ...and that taxes 6 weeks....
I suspect that it perhaps has something to do with Al having reflection properties required for purposes of astronomic observation.
I'm sure most telescope mirrors have protective coatings to protect the aluminium layer.
If amateur reflector telescopes have that, I don't see why these more expensive ones wouldn't.
What if a bird poops on the mirror during the transfer back to the telescope?
+MaxFist I guess at that altitude you don't have birds flying overhead.
I would imagine theyde chuck on a bug ol screen protector on the way back (probably similiar in size to a Galaxy S5
Why not planned obsolescence in science equipment if it progresses other fields so much, as we the masses are lead to believe?
Two minute commercial for 4 and half minute video.
Brady what does "a scientific way" actually mean? Perhaps "highly technical?"
It might be you actually mean the maintenance personal are performing a scientific experiment on the mirror.
+Kawitamamayi it means a serious, rigorous and intelligent way to do things
Your TAX Euros at work.
+Baerchenization yeah... shame so few of them go towards that
rpbsjy
if that's what it takes for them not to sell all Acts to the highest bidder from the lobbyists, so be it
it's enough to look at US what the alternative looks like - Robocop in the making
Censor much? Or why do you delete discussion?
Think: Just 1 speck of dust and you could lose a Whole Galaxy! (or create a new one!) XD
Tell 'em.
BS. you just lose a bit of contrast is all.
Not really, you may lost a really tiny amount of light and contrast but that's it.
There's a story about a telescope mirror that was shot with a gun (by someone really angry at the universe I guess), and besides a few bullet holes, the telescope continued to work fine.
Just google "The McDonald gun shooting telescope".
I'm going to steal one, not because I want it, not because I don't want them to have it, I am going to steal it just for the challenge of stealing it, and I am going to do it without damaging the mirror at all, because that is the real test of being a sneaky thief,,,, I think I've been playing video games to much....
Kind of overwatch payloads :-)
I always thought that beowding was spelt building and pronounced with the "L" sound before the letter "d". Also, I used to think that a mirrah had an "R" sound at the end of it - Mirror. Are they now silent letters or is it just the lazy speech pattern of the Brits?
Aluminum. When will you Brits admit that its pronounced ALOOMINUM. Not ALUMINIUM!
+Desertwhale Nope :)
Aluminium... why? because uranIUM, titanIUM, cesIUM, californIUM, etc etc....... Well there is platinUM so I'll give you that one. Honestly though, it's name was fiddled about with so much when it was first named, both are ok for everyday use.
Aluminium n; -s, no Pl.; CHEM. aluminium, Am. aluminum
How about making a Biophile channel for biology?