Inside the VLT (UT4) - Deep Sky Videos

[@y2kenh]

they are so high. i believe during construction, the trucks hauling stuff up had special sealed cabs, sort of like airplane cabins, so the drivers wouldnt pass out.

[@steelshade]

I tutor Geometry students and the VLTs are an excellent example of Geometry in action! Rotating circles, sliding parallel lines, and structural triangles everywhere you look!

[@TheFakeVIP]

Doesn't watching footage of this magnificently engineered instrument make you proud of humanity and what we can achieve?

[@PetrFlosman]

TheFake VIP yes it does but at the same time it’s kinda sad that 95% people probably don’t even know or care about this.

[@Jasruler]

Petr Flosman even if that estimate were accurate, that still leaves 350,000,000 people who know and care about the VLT. That's not too shabby. Humans are amazing.

[@Philc854]

A most informative video. Sometimes a simple 'walk-around' and running desciption is all that is needed to answer so many questions. That is your forte as a science journalist, Brady. Thanks. More please!

[@DeepSkyVideos]

we'll be doing a video on that!

[@BunnyRaptor]

Wow the time lapse at 5:15 really shows how much the moon affects things.

[@Starchface]

The laser is used to create what is called an artificial guide star. A guide star provides a fixed reference point for adaptive telescope optics in correcting for atmospheric disturbances. In some parts of the sky no suitable natural star is available, so an artificial "laser guide star" is created. There are two main types of laser guide stars: Rayleigh, and the superior sodium guide star (used by VLT). A yellow laser is used to excite atmospheric sodium atoms starting at about 90km altitude.

[@Esudao]

the stars in the picture are very bright, so I guess the exposure time of the picture was long enough so the little lighting the laser does on the particles in the air could accumalte to something visible. but that's only a guess. Would be interesting to know how long brady could hold that pose at 0:48 ;)

[@DeepSkyVideos]

thank you for watchng

[@DeepSkyVideos]

glad you liked it!

[@Plerion]

Are you referring to laser pointers? The VLT system consists of a high power 25 W 589 nm laser, so it's in the visible region of the spectrum and it's powerful enough to excite a band of sodium atoms in an upper layer of the atmosphere (90 kms up). Common laser pointers also are in the visible spectrum but cannot exceed the ~5 mW legal limit (i.e. the VLT laser is ~1000x stronger).

[@insu_na]

When you see the laser beam in this video its either a timelapse, with many frames cut together or an image with long exposure, making the effect even more visible. This laser was designed however to be very visible in the first place, so that the telescope can pick it up

[@wolfman0775]

the beam illuminates dust and water vapour particles in the air meaning you can see the path of the beam, its the same with all lasers, you just dont see it so well with less powerful ones like cheap laser pointers (but it looks amazing with a 200mW green laser pointer)

[@hj45lp]

Great video, thanks for sharing! A question: how do they clean the dust off these large mirrors? Thanks!

[@SN2D]

In wich video do you talk about the laser from UT 4?

[@smunoz08]

I've had the luck to stare at the sky in that particular area of Chile, just with bare naked eyes, and it's mind blowing! The clarity of the skies is so impressive! No wonder they decided to build those telescopes there.

[@AbhijeetBorkar]

We are currently using VLT to observe the center of Milky Way. :D

[@mandydax]

the beam is actually 4 20-watt lasers, and that is a long exposure. There will be scattering, even at that altitude, that allows it to be imaged. I'm sure Brady will explain when he covers the guide star system. I'm really interested in seeing that video.

[@AutoPsychotic]

I suppose that would depend on the concentration of visible particles in the atmosphere off of which it reflects or refracts. Keep in mind all those photos you see of the laser clearly visible coming out of the telescope are long exposure photographs; it wouldn't look like that to the naked eye.

[@CursedJoker]

It is used to probe the random distortions introduced by the atmosphere. Since a laser is a straight line to a very high level of precision, by looking at how its light gets distorted you can get a lot of data to correct those distortions in the actual light the telescope is interested in.

[@SpiritofthePoor]

I believe you are seeing Rayleigh scattering of the laser as it passes through atmospheric gases. This is more visible for shorter wavelengths like green or blue than red, 589.2nm in this case.

[@DeepSkyVideos]

couple of weeks ago I think - I'll be back!

[@TheLukeBrown]

really interesting video Brady. thanks for sharing. great to see inside these incredible places!

[@adamtuft]

Brady, when were you in Sheffield? Come back for more videos please!

[@beardymonger]

Google purchase of KZbin back when is gloriously justified. Thanks Brady. Amazing.

[@PoweredMinecart]

Sorry if these seems ignorant, but are they not allowed to turn on their full lights when driving to the telescope because it will interfere with the telescope or because it can blind oncoming traffic?

[@DeepSkyVideos]

more on that soon

[@SharpBarb]

I'd love to see a video about the Adaptive Optics used to reduce atmospheric effects on the telescope. It's a pretty cool technology.

[@thany3]

That's a bit more than your average 300mm catadioptric camera lens... But why so big? Just to catch more light, or does its size serve an additional purpose?

[@claudioarena6656]

with an off-axis reflector, while you don't get the obstruction from the secondary mirror, you get a lot more optical defects coming into play (and - I believe that collimating it is also way more difficult - if not impossible). You get a lot of coma, as well spherical aberration. That's fine for a cheap little telescope (and the advantages might be worth it - it won't be of superb quality anyway), but for anything serious...you can't use that configuration :)

[@Roedygr]

I would like to see a list of the largest telescopes and the date of inauguration.

[@cpt_nordbart]

Brady sure knows a lot about optics. I wonder why that is... :)

[@Deuce1042]

Man I wish skies were that clear where I live. Perfect place for astronomy. Clear skies and dry.

[@no_more_free_nicks]

You had a lot of fun there!

[@DeepSkyVideos]

they are smart enough to make sure I understand!? And if I don't, I ask more questions until I do! :) I do use web resources, etc, sometimes to check facts and add extra info.

[@ninjaplease123]

Finally. A new video from dsv :)

[@ig7157]

Where is the electricity generated for the telescopes?

[@hrgwea]

It's generated at the base camp where all the personel live, sleep, eat, etc. It's really like a small town.

[@hjembrentkent6181]

@@hrgwea I think Paranal gets power from the chilean grid now.

[@DeepSkyVideos]

cheers

[@FelipeZucchetti]

Wow...thanks Brady...really nice video...

[@mikecurtis389]

Amazing the way it works, technology at its best.

[@Melthornal]

So, Brady, if you were to have one telescope this size, and it were to zoom in as much as it can, how long would it take to cover the entire night sky? Or at least the sky it can see from that position on Earth.

[@bongan]

10:32 "5 million light years - close by for a galaxy, quite far away for a spa"

[@DasPuppy]

long term exposure also captures the not so few photons deflected in all directions by the atoms/particles in the athmosphere...

[@gab1t0w]

Hi, Brady!. Are you planning on doing a video about the soon to come comet Ison (C/2012 S1) and posibbly Magnitudes and the Roche limit... etc etc.. ? thanks!!

[@Chlorate299]

I'm sure there's a good reason for it...but I'll ask anyway. Why, in Newtonian reflecting telescopes, do they not use a primary mirror with a focal point that is offset from the field of view? (i.e. why not an off-axis reflector)

[@SolarMoth]

This video is great! So in depth.

[@bdm1019]

I have been to this place. What an amazing day it was

[@kurtilein3]

the laser is just really, really strong. ive seen that with different lasers in reallife quite often. like an art project connecting different high buildings with green lasers; really visible even with the light pollution in the city. also there are now handheld lasers strong enough for this.

[@AbhijeetBorkar]

We have to send proposals to get time. The best proposals are given time. Non-optical astronomy doesn't usually work on monetary basis.

[@Tonjevic]

How do they keep the mirror clean? Presumably the image degrades as dust settles on the optics?

[@TheMotU92]

can't wait for the next videos :)

[@BorealSelfReliance]

I would have never thought that actuators would have been required to keep the shape of the mirror, now that is pretty cool!

[@astronotyet]

It is used for removing the effects of atmospheric distortion. Read about Adaptive Optics in Wikipedia.

[@TilmanBaumann]

Great animations for the light path

[@rebmcr]

Why do the wind shutters open one by one? Even if they sometimes only open half of them, why can't they just open all the selected ones simultaneously?

[@maxkamarov514]

Please, I would like to know more about the laser in UT4.

[@JosephCoxH]

I imagine it's because tiny dust particles scatter a bit of the light, which is why you can see a laser at all for the most part.

[@TheIndinapolis2]

Hi Brady, I'm a high school student in the US and my dream is to work as an astrophysicist hopefully in a large telescope just like this one. I have a long ways to go but is there any chance you know how the workers at the telescope got jobs there? Meaning degrees, qualifications, etc. Any response would be great, I love your videos and keep up the great work!

[@fredlllll]

long time exposure. also a strong laser lights up more particles in the air

[@teasesTheBear]

A tiny fraction of the laser light scatters on particles in the air. I could imagine water vapor, dust or other aerosols. Usually one would not see the laser with the naked eye though, I assume. However, if the exposure long when taking a photo, the scattered laser light is accumulated and becomes visible.

[@TheEnterShepman]

Nice :) I just watched the "VLT Opening" video

[@slavkovalsky1671]

Got really curious about the original science case for the HST: what WERE the boring and/or impossible things it was originally designed to do? A google search didn't turn up anything... And tips on where to find this info would be greatly appreciated.

[@TheVergile]

is the whole dome under positive pressure? I always assumed them being in a desert kinda meant problems with sand/dust in the air

[@FOETRAIN]

Excellent video , much appreciated :)

[@TheManSand322]

how often do the mirrors need to be cleaned ?

[@mariesoullier]

Why do you have to wear a hardhat? What are they worried might fall on you?

[@kf160k160]

What is the laser for actually? I know it can use to measure distance between moon and earth but what else it use to measure?

[@MrRobinhalligan]

did they let you fire the death ray?

[@superdau]

Combine the dust/maybe even molecules that scatter light in the atmosphere with a very powerful laser (you can tell that by having it's own cabin this is not your average laser pointer ;) ) and very long exposure times and you'll always see the laser.

[@TheKelvinator11]

how do they keep the mirrors clean?

[@ArichManas]

Air refracts light, no matter what the intensity is. It is such a powerful laser that it reflects enough for the human eye to easily see it!

[@steadilyebbing]

Short answer: It creates kind of an artificial star in the upper atmosphere that wiggles about due to atmospheric effects. By noting how your fake star moves about you can correct the wiggles when you're looking at real stars.

[@CreamAle]

hey brady, i know you're a pretty smart chap.. but, when you interview the folks are you ever lost in what they are saying? if so, after the interview do you ask more? or perhaps even google it while editing? always wondered that but never asked.

[@oceanceaser44]

why would it be so hard to see from that angle?

[@claudioarena6656]

I wonder how you actually move the telescope in altitude. For sure you don't use the classical worm drive...I'm think I saw something like...a chain (such as a bicycle chain). I'm very interested to know, if anybody can tell me :)

[@Chlorate299]

Ah I see, that makes sense. I knew there would be a good reason for it. Many thanks.

[@abex701]

Hey Brady, how's Chile?

[@ZestyCrunchy]

And what's the laser for?

[@sachiperez]

more please! :)

[@Ferreus1]

what is the lazer for?

[@hrgwea]

Why is the laser visible? Light going through clean air shouldn't be visible at all, right?

[@odourpreventer]

How come the laser beam can be seen so clearly. Shouldn't it be more or less invisible, at least at that angle?

[@Teapasoo]

Why does UT4 shoot a laser at night?

[@Jbmz03]

Now we all want to see the laser video :D

[@celtgunn9775]

Too bad Zooniverse isn't still running the programs to find things in the galaxy. I loved searching for galaxies and the bubbles. Great video showing this telescope Brady.

[@CreamAle]

gotcha, well keep it up mate!

[@glorious_help]

motion sick... Great stuff though, keep going!

[@kurtilein3]

you can see it quite well with the naked eye. the laser just needs to be powerful enough; a handheld green or blue 5 watt laser will definitively show this effect. like: watch?v=yDSdChJI5dA

[@theonlyari]

In a vacuum, yes, it would be invisible. Since we, fortunately dont live in a vacuum, there are impurities in the air, like dust, that reflect the light towards the camera.

[@3doog]

Why do you have to drive slowly?

[@superdau]

You can get away with much smaller components. To move all at once you'd need a much bigger motor, much stronger rails and bearings. As it is now you just need a small bearing to roll on the slide below. As an astronomer you pretty much know when the sun will set ;) , so just start sooner with opening to be ready. The telescope must adapt to the outside temperature anyway and opening them one by one may even has the advantage of not letting too much air rush in at once and blow dust everywhere.

[@brandonthesteele]

Those scopes are a loooooot bigger than I thought.

[@BongboBongbong]

+Jaxsongaming25 And soon ... the EXTREMELY LARGE european telescope (E-ELT)!

[@aurelia8028]

it's actually "European-Extremely Large Telescope"

[@DeepSkyVideos]

you're welcome

[@ericvilas]

I guess it's so powerful it ionizes the air?

[@subi7o]

"And there's still plenty of other universe our there." Hah, yeah, I guess you could say there is!

[@ghuegel]

There's a terrific podcast called "Astronomy Cast"; it's free on iTunes. They cover all sorts of astronomy-related topics, and there's been at least one episode on what a person needs to do to become an astronomer (it is not easy!). Sounds like you'd really enjoy it and get a lot out of it. Check it out.

[@Elios0000]

its to compensate for the the atmosphere

[@forloop7713]

Do they ever clean the mirror

[@samstrobelight]

I bet you love traveling to make videos, I'm kinda jealous!

[@IstasPumaNevada]

I'd say it's so it doesn't introduce light pollution that will interfere with the telescopes' operation.