The largest telescope ever built

[Robert W]

would it be fun if you got the inside scoop on the super large telescopes?
It was for me when I watched the video below.
Points to be discussed or others:
Why are they up so high on Earth?
How accurate are they?
What is the mirror coated with?
And you can come up with a lot more.

 

[LuckyDuck]

We need to stop wasting money on these large land-based telescopes and build a "Gravity Telescope" to be able to see the exo-planets.
Also, there needs to be more investment in and joint research on FTL space propulsion.

 

[Robert W]

We need to stop wasting money on these large land-based telescopes and build a "Gravity Telescope" to be able to see the exo-planets.
Also, there needs to be more investment in and joint research on FTL space propulsion.

“We want to take pictures of planets that are orbiting other stars that are as good as the pictures we can make of planets in our own solar system,” said Bruce Macintosh, a physics professor at in the School of Humanities and Sciences at Stanford and deputy director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). “With this technology, we hope to take a picture of a planet 100 light-years away that has the same impact as Apollo 8’s picture of Earth.”

The catch, at present, is that their proposed technique would require more advanced space travel than is currently available. Still, the promise of this concept and what it could reveal about other planets, makes it worth continued consideration and development, said the researchers.

 

[ReinyDays]

"How high" is a thinner atmosphere ... and that means more star light can be captured by your mirror ... aluminum is used generally, and equipment for depositing that thin layer is in the observatory basement ... just point the telescope straight up and lower the glass into the vat of steaming sulfuric acid or whatever they use ...

Not sure what you mean by how accurate ... amateur jobs in a garage have to be true to within a 1/4 wavelength of light, 75 nanometers for visible light telescopes, closer to a foot for radio ...

I might be wrong ... but I think a single telescope can only resolve pin-points of light from stars ... no disks ... it takes a sophisticate array of telescopes to get any more resolution ... or one above the atmosphere ...

Beautiful here Friday morning, and Sunday morning was just as clear and bright ... it was raining on Saturday during the eclipse ... Jefferson is where evil star-gazers are sent as Hell ... rains every day all day long ... especially during solar eclipses ...

 

[Robert W]

"How high" is a thinner atmosphere ... and that means more star light can be captured by your mirror ... aluminum is used generally, and equipment for depositing that thin layer is in the observatory basement ... just point the telescope straight up and lower the glass into the vat of steaming sulfuric acid or whatever they use ...

Not sure what you mean by how accurate ... amateur jobs in a garage have to be true to within a 1/4 wavelength of light, 75 nanometers for visible light telescopes, closer to a foot for radio ...

I might be wrong ... but I think a single telescope can only resolve pin-points of light from stars ... no disks ... it takes a sophisticate array of telescopes to get any more resolution ... or one above the atmosphere ...

Beautiful here Friday morning, and Sunday morning was just as clear and bright ... it was raining on Saturday during the eclipse ... Jefferson is where evil star-gazers are sent as Hell ... rains every day all day long ... especially during solar eclipses ...

They have a special designed washer to remove the aluminum. Then they slowly deposit atoms of aluminum until they reach the desired reflection state.

 

[ReinyDays]

They have a special designed washer to remove the aluminum. Then they slowly deposit atoms of aluminum until they reach the desired reflection state.

Home made mirrors can be silvered at home in just a water bath ... however, to get the aluminum into her vapor state, and a good even deposition, we have to reduce pressure ... and it's a vacuum chamber built into the basements of these big telescopes ... multi-telescope facilities might have a centralized building with the vacuum chamber ... aluminum is slow to react with atmospheric oxygen, but it does react and ruin the reflective surface of the mirror ...

Cheaper than having to re-silver your mirror every other month or so ... maybe get a year out of a home silvering job ... one is always better off shipping your mirror off to be aluminized ... just pay the money cheapskate ...

 

[Robert W]

Home made mirrors can be silvered at home in just a water bath ... however, to get the aluminum into her vapor state, and a good even deposition, we have to reduce pressure ... and it's a vacuum chamber built into the basements of these big telescopes ... multi-telescope facilities might have a centralized building with the vacuum chamber ... aluminum is slow to react with atmospheric oxygen, but it does react and ruin the reflective surface of the mirror ...

Cheaper than having to re-silver your mirror every other month or so ... maybe get a year out of a home silvering job ... one is always better off shipping your mirror off to be aluminized ... just pay the money cheapskate ...

They explain that in the video. I wish those interested in this topic would watch all of the video. They resilver the mirrors every two years and have an extremely scientific viable way to do it.

 

[Robert W]

Home made mirrors can be silvered at home in just a water bath ... however, to get the aluminum into her vapor state, and a good even deposition, we have to reduce pressure ... and it's a vacuum chamber built into the basements of these big telescopes ... multi-telescope facilities might have a centralized building with the vacuum chamber ... aluminum is slow to react with atmospheric oxygen, but it does react and ruin the reflective surface of the mirror ...

Cheaper than having to re-silver your mirror every other month or so ... maybe get a year out of a home silvering job ... one is always better off shipping your mirror off to be aluminized ... just pay the money cheapskate ...

This was about the largest ever telescope. More than likely per the video it will be as big as possible. The video explains resilvering as experts do it.

 

[JohnDB]

Large telescopes require multiple mirrors to be large enough. Even the large ones in orbit.

This also requires stable temperatures where half a degree difference means a lot. When you are magnifying a spot a few million light years away and magnifying it a few thousand times....slight degree changes matter....so does interference of "cosmic dust" from comets and solar flares...even asteroid collisions.

So actually a telescope in our orbit is too unstable for this size and type of telescope. Have to put one beyond the asteroid belt to see accurately for less interference and have it orbit successfully. (Past Mars)

 

[Robert W]

Large telescopes require multiple mirrors to be large enough. Even the large ones in orbit.

This also requires stable temperatures where half a degree difference means a lot. When you are magnifying a spot a few million light years away and magnifying it a few thousand times....slight degree changes matter....so does interference of "cosmic dust" from comets and solar flares...even asteroid collisions.

So actually a telescope in our orbit is too unstable for this size and type of telescope. Have to put one beyond the asteroid belt to see accurately for less interference and have it orbit successfully. (Past Mars)

That is true enough. Yet this worlds largest telescope is being built and the scientists and astronomers expect to use it. It is said to have more power than the Webb telescope that was launched not long ago that is very productive.

The problems you bring up are all solved by this telescope and also the others on the top of the mountain in Chile.

One thing I hoped would happen is we would all brush up on this so we knew the latest developments.

 

[Nobody911]

would it be fun if you got the inside scoop on the super large telescopes?
It was for me when I watched the video below.
Points to be discussed or others:
Why are they up so high on Earth?
How accurate are they?
What is the mirror coated with?
And you can come up with a lot more.

Using telescopes is like studying history. lol.

When we observe objects or events through a telescope, we are actually seeing them as they were in the past, not as they are in the present or will be in the future. This is because light takes time to travel from its source to our eyes or telescopes, and therefore, the light we receive from distant objects or events is delayed. The farther away an object is, the longer the delay in the light reaching us, and thus, the further back in time we are seeing.

For example, when we look at stars in the night sky, we are seeing them as they were many years ago because the light from those stars takes a significant amount of time to reach us. Similarly, when we observe distant galaxies, we are seeing them as they appeared millions or even billions of years ago.

This concept applies not only to telescopes but also to our everyday perception of the world. We are always perceiving the world around us with a slight delay due to the time it takes for light to reach our eyes.

 

[ReinyDays]

Large telescopes require multiple mirrors to be large enough. Even the large ones in orbit.

This also requires stable temperatures where half a degree difference means a lot. When you are magnifying a spot a few million light years away and magnifying it a few thousand times....slight degree changes matter....so does interference of "cosmic dust" from comets and solar flares...even asteroid collisions.

So actually a telescope in our orbit is too unstable for this size and type of telescope. Have to put one beyond the asteroid belt to see accurately for less interference and have it orbit successfully. (Past Mars)

Just a reminder there's folks on these boards with telescopes ... and they know more about these machines than I ...

Temperature differences across a small 6" or 8" mirror would make a huge difference, but this never happens under normal usage ... the larger telescopes are more sensitive, but in the context of gigantic vacuum chambers underneath the speculum, climate control inside the building is easy ... and interplanetary debris is far less a problem than our own atmosphere ...

Stability is a big deal ... especially for our smaller backyard 'scopes ... one idea helps to illustrate the solution ... take an old Chevy 350 V-8 automobile engine and set it up, upside down, with the crankshaft pointed at the North Star ... then pour a couple yards of concrete to hold it in position ... the crankshaft is our polar axis and we can build our equatorial axis easy enough and ... presto ... a one ton German mount that the breeze won't rattle around ... the principle being the heavier the telescope, the less jiggling it'll do when the camera's shutter is open ...

We avoid all this by putting telescope in Earth's orbit ... no wind, no children, no semi-trucks ... and most important, no atmosphere ...

This is the biggest telescope because there's no point building them bigger until we get access to the Tibetan Plateau ... these high mountain-top usually don't even have goat paths to the top ... let alone the Interstate-grade freeway needed to bring materials up ... 400" mirror can't be carried by hand ... drive up San Diego County Road S6 ... yeah ... part of the cost of the Palomar Telescope ...

=====

So much for late 17th Century technology ... real astronomers use telescopes in pairs or arrays ... the Keck Observatory in Hawai'i is a good example ... TWO of these 400" monsters ... we know the distance between the two very very accurately and that ... er ... well ... frankly I don't know ... here's the Wikipedia article ... I'd rather bail out a septic tank then figure this shit out ... talk about hokay finokay ...

Astronomical interferometer - Wikipedia

en.wikipedia.org

See where it explains baseline ... the LIGO experiment had one detector in Louisiana and the other in Washington State ... at scale, we'd want this to be several Neptune-orbit diameters ... anything within the heliosheath ... easy enough to attach EM telescopes and use the same techniques ...

Again, just a reminder there's folks on these boards with telescopes ... and they know more about these machines than I ...

 

[JohnDB]

Just a reminder there's folks on these boards with telescopes ... and they know more about these machines than I ...

Temperature differences across a small 6" or 8" mirror would make a huge difference, but this never happens under normal usage ... the larger telescopes are more sensitive, but in the context of gigantic vacuum chambers underneath the speculum, climate control inside the building is easy ... and interplanetary debris is far less a problem than our own atmosphere ...

Stability is a big deal ... especially for our smaller backyard 'scopes ... one idea helps to illustrate the solution ... take an old Chevy 350 V-8 automobile engine and set it up, upside down, with the crankshaft pointed at the North Star ... then pour a couple yards of concrete to hold it in position ... the crankshaft is our polar axis and we can build our equatorial axis easy enough and ... presto ... a one ton German mount that the breeze won't rattle around ... the principle being the heavier the telescope, the less jiggling it'll do when the camera's shutter is open ...

We avoid all this by putting telescope in Earth's orbit ... no wind, no children, no semi-trucks ... and most important, no atmosphere ...

This is the biggest telescope because there's no point building them bigger until we get access to the Tibetan Plateau ... these high mountain-top usually don't even have goat paths to the top ... let alone the Interstate-grade freeway needed to bring materials up ... 400" mirror can't be carried by hand ... drive up San Diego County Road S6 ... yeah ... part of the cost of the Palomar Telescope ...

=====

So much for late 17th Century technology ... real astronomers use telescopes in pairs or arrays ... the Keck Observatory in Hawai'i is a good example ... TWO of these 400" monsters ... we know the distance between the two very very accurately and that ... er ... well ... frankly I don't know ... here's the Wikipedia article ... I'd rather bail out a septic tank then figure this shit out ... talk about hokay finokay ...

Astronomical interferometer - Wikipedia

en.wikipedia.org

See where it explains baseline ... the LIGO experiment had one detector in Louisiana and the other in Washington State ... at scale, we'd want this to be several Neptune-orbit diameters ... anything within the heliosheath ... easy enough to attach EM telescopes and use the same techniques ...

Again, just a reminder there's folks on these boards with telescopes ... and they know more about these machines than I ...

Most earth based large telescopes are put out in the middle of nowhere....like the desert or ocean (Hawaii is a classic example)

This way light pollution, smog, and etc won't interfere so much.

Those out in the desert of Nevada or Arizona who have big telescopes use an average individual sized portable telescope as a spotter scope. The area their big telescope is mounted to is a huge, deep, bit of concrete slab so as to hold their large telescope steady.

 

[ReinyDays]

Most earth based large telescopes are put out in the middle of nowhere....like the desert or ocean (Hawaii is a classic example)

This way light pollution, smog, and etc won't interfere so much.

Those out in the desert of Nevada or Arizona who have big telescopes use an average individual sized portable telescope as a spotter scope. The area their big telescope is mounted to is a huge, deep, bit of concrete slab so as to hold their large telescope steady.

Great points ... Palomar is limited use today except the view of them 25 million or so inhabitants of Southern California ... very impressive ...