<p><a href="https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5487/1/Buyers-guide-to-telescopes-at-the-best-sites--Dome/10.1117/12.596320.full?SSO=1" rel="nofollow noreferrer">This 2004 article</a> although a little dated now, discusses the relative merits of three possible novel sites for new major optical/IR telescopes: Dome A in Antarctica, the South pole of the Moon, and the Earth-Sun L2 point (or an orbit around it). Each is best for different purposes. A particular attraction of the Lunar site is the ability to stare at the same part of the sky for very long periods to detect very faint objects.</p>

CC BY-SA 4.0
2018-06-07T10:34:08.780Z
2018-06-07T10:34:08.780Z
Steve Linton
<p>Telescopes on the moon are a <strong>fantastic idea</strong>. If you "thought it up yourself" congratulations, because it's a great idea for the future.</p>

<p>As you may know we already have many fantastic telescopes in space (that is to say, generally orbiting or near our Earth). The <strong>next step</strong> would be telescopes on the Moon. (It is far, far, harder to build one on the moon, than simply lift one up to orbit.)</p>

<p>You can easily find many beginning studies about it; for example <a href="https://www.space.com/5628-nasa-envisions-huge-lunar-telescope.html" rel="nofollow noreferrer">here</a> is one by NASA on your great idea, from ten years ago!</p>

<p>Your idea is a good one, and hopefully it comes sooner rather than later. I bet we are 30 years away from telescopes on the moon. But they will come.</p>

CC BY-SA 4.0
2018-06-07T02:10:42.117Z
I don't know why you'd call the Moon the "next step".  I voted you up for your NASA article though.  That pretty well covers it.  The point is that a telescope, built out of lunar material, could be larger and set up more cheaply than anything we can launch from Earth . . . in that sense, I guess it is a next step but there are several next steps already on the way, the next one is James Webb, that will unfold in space if all goes according to plan.   The real advantage to the Moon is lunar material could be used, so stuff doesn't need to be launched from Earth.
userLTK
CC BY-SA 4.0
2018-06-07T10:12:05.200Z
Nanotubes? In the resin mirror? Sounds silly. Why? Nanotubes, carbon fiber is more rigid than steel. Aluminium vapor deposition? On the moon? That researcher needs a 20meter mirror to be taken seriously. Better build microscopes for malians and sudanese first or you can make a ladder to the moon from them?
bandybabboon
CC BY-SA 4.0
2018-06-07T11:08:20.553Z
Building a lunar base is actually scifi, a dark side of the moon base with the industrial capacity of building high-tech telescopes is more suited to [WolrdBuilding SE](https://worldbuilding.stackexchange.com/) than [Space Exploration SE](https://space.stackexchange.com/)
jean
CC BY-SA 4.0
2018-06-06T22:10:59.997Z
2018-06-07T11:31:10.363Z
2018-06-07T11:31:10.363Z
Fattie
<p>There are advantages and disadvantages.</p>

<p>Earth based telescopes have disadvantages because of the atmosphere, which blocks some light and it blocks some wavelengths almost completely and it also bends the incoming light.   Some of the atmospheric displacement can be fixed with modern computers, so Earth based telescopes have improved significantly over the last 20-30 years, but they still have the disadvantage Earth's atmosphere blocking some of the light coming in from space.  Today's Earth based telescopes are as good as Hubble (I read that somewhere) at least in the visible spectrum, in large part because of computerized imaging.  When Hubble was launched (and fixed) at the time if was lightyears better than anything on Earth.  Today it's close.</p>

<p><a href="https://www.space.com/6716-major-space-telescopes.html" rel="nofollow noreferrer">Chandra and Spitzer</a> see in wavelengths that don't make it to Earth, so they need to be in orbit to work.   James Webb will also view in the infra-red as well as visible wavelengths, so it needs to be in space to take advantage of it's infrared imaging. </p>

<p>Space is much better because it gets a much cleaner picture and it receives all wavelengths.   There are disadvantages to being in space too, like cosmic rays, solar storms and the occasional near-light-speed proton but on average, space is better than Earth and the surface of the Moon is similar to being in space due to there being essentially no atmosphere.</p>

<p>A big problem with telescopes in space is that launching that much material is very expensive.  It costs about $10,000 per pound to launch something into space.  That's why there's so few you can count space telescopes on your fingers (fingers and toes actually, <a href="https://www.space.com/6716-major-space-telescopes.html" rel="nofollow noreferrer">I think there's 13</a>).</p>

<p>It's also important to keep large telescopes somewhat cold.  (<a href="https://jwst.nasa.gov/sunshield.html" rel="nofollow noreferrer">James Webb will have a large sun shield</a>).   That's especially important for infrared imaging. Provided the area is shaded, the moon will remain sufficiently cold.</p>

<p>The big advantage the Moon has is that it's full of silicon, which is what mirrors are made of, so by using lunar material, much less stuff needs to be launched and that saves a ton of money and increases the size of this theoretical telescope.   That's the real advantage.  We can't launch a 100 or 200 foot telescope from Earth because it's too big, but we could in theory, built one that size on the moon because there's lots and lots of stuff to use.   </p>

<p>A smaller advantage is that the body of the moon acts as a shield for what's below it, but the real advantage is that the Moon is made of stuff that can be turned into a telescope.   Really any large body a few miles in diameter would work, though working on a surface with gravity might be easier.   Personally I think Ceres would be a great place to build.  Very low gravity (but enough where you can set things down and not worry about them bouncing away) farther from the sun so a smaller sun-shield.   Any reasonably large body in space could theoretically be used to build a telescope.</p>

<p>The moon, however, is closer, so it's both more easily repaired and it's close enough that it's easier to transmit images back to Earth as opposed to a Phobos based or Ceres based telescope.</p>

<p>This shouldn't be mistaken for easy though.  It's never been done and might run into unanticipated problems and end up being quite difficult, but it's a nice idea.   </p>

CC BY-SA 4.0
2018-06-07T09:55:15.707Z
The silicon is full of feldspar, pure silicon on earth comes from geothermal water and sea action. Youd need hot crucibles of moon rock and refine feldspar silicon mix, un unkown industry. Youd need gold, aluminium, vapor deposition chambers, dust free clean-rooms, the moons dust is abrasive. A flintstonoscope on the moon would not be optimal use of money. After building the silicon refinery for 10billion dollars. The list of costs would exceed 200 billion in todays money... lifting machines,cranes, it would be cheaper to make homes there than big machines.
bandybabboon
CC BY-SA 4.0
2018-06-07T11:23:21.103Z
It would be insanely expensive to set up that manufacturing infrastructure just to build a telescope. Of course, if you were building a base big enough to warrant that setup, or a long-term colony, then sure you might as well build a scope at some stage.
PM 2Ring
CC BY-SA 4.0
2018-06-07T14:55:56.467Z
@com.prehensible  I was going off this NASA article, which you critiqued in the other answer.    https://www.space.com/5628-nasa-envisions-huge-lunar-telescope.html   I have no idea how feasible it actually is, but I did mention that it's never been done and could be quite difficult.   Probably not something we'll see anytime remotely soon, if at all.
userLTK
CC BY-SA 4.0
2018-06-07T02:05:08.117Z
2018-06-07T02:05:08.117Z
userLTK
<p>It's very unlikely that large optical telescopes will ever be built on the Moon, because the Moon is almost the worst possible place to build them. (The surfaces any of the  planets other than Earth are worse.)  It has no particular advantages over orbit and costs a lot more to build there.</p>

<p>The Moon looked like a good location when observatory technology was film-based, because observatories required people and people needed a base to live in and work best under gravity.  But we now have the technology to shade an orbiting telescope from the Sun, point it exquisitely accurately, and take endless photos without changing the film -- all in orbit.  Orbit is easier to get to than the Lunar surface -- even the Webb (should it ever launch) which will be parked a million miles from Earth, is easier to get to than the surface of the moon.</p>

<p>If we had the space capabilities to build a giant reflector on the Moon, we could build an even bigger and better one in orbit for the same cost.</p>

<p>You spoke of FAST. FAST is a radio telescope. It's likewise much cheaper to build radio telescopes in orbit than on the Lunar surface. The one possible advantage of the Moon is that the far side of the Moon might have advantages of being especially radio quiet.</p>

<p>But even there, it seems likely that any space radio telescope would be a large array of radio telescopes joined to form a giant synthetic aperture, and that would almost certainly want to be much larger than earth-based instruments -- for which the Moon is already too small.</p>

CC BY-SA 4.0
2018-06-07T05:41:28.977Z
+1 for mentioning radio telescope arrays as another example of why the Moon is unrealistic as an option.
Chappo Hasn't Forgotten
CC BY-SA 4.0
2018-06-07T14:51:02.617Z
The only thing I'm not sure I agree with is "build a better one in orbit for the same cost"   When the telescope gets big enough, the primary expense becomes the launching, not the building.   Building on the moon circumvents the launching cost.  Building on any sizable asteroid could work too, but I think some gravitation is a plus in building.  Most asteroids have close to zero gravity.  Apart from that one point, I think your answer is spot-on.
userLTK
CC BY-SA 4.0
2018-06-07T14:56:18.040Z
You don't build it in space in the sense of stacking up bricks and riveting pieces of steel together! A modern telescope is a *very* complex gadget and would be built in pieces by specialists on the ground using millions of man-hours and then launch with final assembly done in space.  In building a big telescope off-earth, gravity is no help at all -- it's a distinct hindrance!
Mark Olson
CC BY-SA 4.0
2018-06-08T18:07:37.797Z
For anything built on moon, the dust must be considered too. Its sharpness without weathered edges causes serious problems both to humans and machines, plus it electrostatically levitates - prone to cling to optics and everything else.
Juraj
CC BY-SA 4.0
2022-01-13T12:15:43.710Z
The JWST has indeed launched, and though it's very early days it seems to have deployed as well as or even better than was expected
Richard Ward
CC BY-SA 4.0
2018-06-07T01:18:38.073Z
2018-06-07T11:55:49.270Z
2018-06-07T11:55:49.270Z
Mark Olson
<p>China's FAST (Five-hundred-meter Aperture Spherical radio Telescope) is the largest radio telescope in the world.(This is huge!!!)
<a href="https://i.sstatic.net/uPEdm.jpg" rel="noreferrer"><img src="https://i.sstatic.net/uPEdm.jpg" alt="enter image description here"></a></p>

<p>As we all know Space Telescopes are better than Earth-Based telescopes always.(Hubble space telescope was such a tremendous success)Even though ground-based observatories are usually located in highly elevated areas with minimal light pollution, but still they contend with atmospheric turbulence, which limits the sharpness of images taken from this vantage point.</p>

<p><em>What if all the space agencies collaborate together to build a telescope half the size of China's FAST in moon(Even smaller than half),even then it will be more powerful than the "FAST" right(because the atmosphere of moon is very less dense)?Will it be impractical?It may take decades to build one but still the outcome will be huge(We may even look and find aliens!!)</em></p>

<p><strong><em>(Taking in account that Elon Musk is already planning Colonization of Mars)This project looks somewhat tamable than that,right?  Is there a possibility of this happening? Is it feasible enough?</em></strong></p>

CC BY-SA 4.0
2018-06-06T19:53:47.283Z
Why you think building it on the Moon is easier/cheaper/better than building it on orbit?
jean
CC BY-SA 4.0
2018-06-06T20:15:44.163Z
@jean i don't think it will be easier.Hubble space telescope is in LEO  and mostly in LEO spacewalks are conducted,so possibility of  building it in higher orbits are ruled out .Now if we build it in LEO,there will be many factors like debris, altitude loss during its run,air drag etc etc.But in moon i think we will have a more stable base to build on. Definitely not expecting it to be cheaper and easier.In moon the building scale/size can be very large i think.And the added bonus will be its gravity(even though its less).And stability is important because i think it take a decade to complete.
Paran
CC BY-SA 4.0
2018-06-06T20:37:44.507Z
Moon got a lot of dust and I don't know we can build anything without get it covered in it. Anyway let's rephrase my first comment: Why do you think it can be scaled up in the Moon? Drag? Debris are a real problem? Why do you think gravity will help and why it will be more stable? It will no be easier to mitigate altitude loss than make a Moon landing? and finally with the same budget why not build a dozen same size telescopes on earth (and keep upgrading and maintaining it)
jean
CC BY-SA 4.0
2018-06-06T21:10:50.030Z
You seem to be talking about telescopes operating in the visual wavelengths but you show a radio telescope. Are you aware of the differences?
Chappo Hasn't Forgotten
CC BY-SA 4.0
2018-06-06T21:14:13.810Z
@Chappo sorry i just wanted to refer to its scale.
Paran
CC BY-SA 4.0
2018-06-06T21:27:35.980Z
@jean According to me It can be scaled up in moon quite easily. For an analogy(this is a horrible analogy and i am so so sorry)-Try building a big book shelf in a swimming pool while floating(wooden parts will also keep floating, it will be quite hard to assemble) and do the same in your workbench. You can leave the bookshelf while it is half completed and go out for a week and still find it in the same condition when  you return back, right? Can it be said the same if you left the shelf in the pool? It will change position? Right
Paran
CC BY-SA 4.0
2018-06-06T21:37:02.063Z
@jean Earth based telescope have many demerits. Space based telescope are much superior-- http://curious.astro.cornell.edu/about-us/121-observational-astronomy/telescopes/general-questions/745-what-are-the-advantages-and-disadvantages-of-using-a-telescope-in-space-intermediate Check it out
Paran
CC BY-SA 4.0
2018-06-06T22:13:08.287Z
@ParanBharali, it is very, very easy to have telescopes in Space.  You just build the scope, then sit it on a rocket, and press the button.  Building a scope on the moon is **incredibly more difficult, and it is more difficult in many, many ways**.
Fattie
CC BY-SA 4.0
2018-06-06T22:16:31.793Z
hi @ParanBharali !  I didn't understand your sentence, but the bottom line is it will be very, VERY difficult to build telescopes on the moon.   But it will come!  Maybe when you are a grandparent.
Fattie
CC BY-SA 4.0
2018-06-07T01:21:24.100Z
@Fattie launching a telescope by rocket limits the size of the telescope to what the rocket can carry.   Actually building one in space you can build much larger.   Rocket launches are limited.
userLTK
CC BY-SA 4.0
2018-06-07T02:07:16.940Z
This probably should be space exploration not astronomy, but it's obviously gotten a lot of attention here.
userLTK
CC BY-SA 4.0
2018-06-07T13:38:33.160Z
@userLTK - you can't "build" anything in space. it's just vacuum.  obviously, as you say, each rocket payload size limits the size of that part you can send up.  if someone wanted to send up a telescope much bigger than JWT they'd send up the parts (2, 10, 100, whatever flights) and **assemble** it.   note that, hauling a factory to the moon is, of course, also obviously limited by the size of the lunar transports
Fattie
CC BY-SA 4.0
2018-06-07T18:06:47.500Z
You may want to read up on *adaptive optics*: https://en.wikipedia.org/wiki/Adaptive_optics
cms
CC BY-SA 4.0
2018-06-08T13:58:18.350Z
Space telescopes are **not *always*** better than Earth-based telescopes. They both have advantages and disadvantages, and whether one is "better" than another ultimately depends on the specific purpose.
Mick
<the-moon><telescope><observational-astronomy><space-telescope><deep-sky-observing>
Is it practical to build a giant telescope in Moon? (Considering the fact that the atmosphere of moon is very rare)
Paran
# Is it practical to build a giant telescope in Moon? (Considering the fact that the atmosphere of moon is very rare)

(Asked by: username_0 on 2018-06-06)

China's FAST (Five-hundred-meter Aperture Spherical radio Telescope) is the largest radio telescope in the world.(This is huge!!!)
[![enter image description here](https://i.sstatic.net/uPEdm.jpg)](https://i.sstatic.net/uPEdm.jpg)

As we all know Space Telescopes are better than Earth-Based telescopes always.(Hubble space telescope was such a tremendous success)Even though ground-based observatories are usually located in highly elevated areas with minimal light pollution, but still they contend with atmospheric turbulence, which limits the sharpness of images taken from this vantage point.

*What if all the space agencies collaborate together to build a telescope half the size of China's FAST in moon(Even smaller than half),even then it will be more powerful than the "FAST" right(because the atmosphere of moon is very less dense)?Will it be impractical?It may take decades to build one but still the outcome will be huge(We may even look and find aliens!!)*

***(Taking in account that Elon Musk is already planning Colonization of Mars)This project looks somewhat tamable than that,right? Is there a possibility of this happening? Is it feasible enough?***

**Tags:** the-moon, telescope, observational-astronomy, space-telescope, deep-sky-observing
> **Comments:**
> **username_1**: Why you think building it on the Moon is easier/cheaper/better than building it on orbit?  
> **username_0**: @jean i don't think it will be easier.Hubble space telescope is in LEO  and mostly in LEO spacewalks are conducted,so possibility of  building it in higher orbits are ruled out .Now if we build it in LEO,there will be many factors like debris, altitude loss during its run,air drag etc etc.But in moon i think we will have a more stable base to build on. Definitely not expecting it to be cheaper and easier.In moon the building scale/size can be very large i think.And the added bonus will be its gravity(even though its less).And stability is important because i think it take a decade to complete.  
> **username_1**: Moon got a lot of dust and I don't know we can build anything without get it covered in it. Anyway let's rephrase my first comment: Why do you think it can be scaled up in the Moon? Drag? Debris are a real problem? Why do you think gravity will help and why it will be more stable? It will no be easier to mitigate altitude loss than make a Moon landing? and finally with the same budget why not build a dozen same size telescopes on earth (and keep upgrading and maintaining it)  
> **username_2**: You seem to be talking about telescopes operating in the visual wavelengths but you show a radio telescope. Are you aware of the differences?  
> **username_0**: @Chappo sorry i just wanted to refer to its scale.  
> **username_0**: @jean According to me It can be scaled up in moon quite easily. For an analogy(this is a horrible analogy and i am so so sorry)-Try building a big book shelf in a swimming pool while floating(wooden parts will also keep floating, it will be quite hard to assemble) and do the same in your workbench. You can leave the bookshelf while it is half completed and go out for a week and still find it in the same condition when  you return back, right? Can it be said the same if you left the shelf in the pool? It will change position? Right  
> **username_0**: @jean Earth based telescope have many demerits. Space based telescope are much superior-- http://curious.astro.cornell.edu/about-us/121-observational-astronomy/telescopes/general-questions/745-what-are-the-advantages-and-disadvantages-of-using-a-telescope-in-space-intermediate Check it out  
> **username_3**: @ParanBharali, it is very, very easy to have telescopes in Space.  You just build the scope, then sit it on a rocket, and press the button.  Building a scope on the moon is **incredibly more difficult, and it is more difficult in many, many ways**.  
> **username_3**: hi @ParanBharali !  I didn't understand your sentence, but the bottom line is it will be very, VERY difficult to build telescopes on the moon.   But it will come!  Maybe when you are a grandparent.  
> **username_4**: @Fattie launching a telescope by rocket limits the size of the telescope to what the rocket can carry.   Actually building one in space you can build much larger.   Rocket launches are limited.  
> **username_4**: This probably should be space exploration not astronomy, but it's obviously gotten a lot of attention here.  
> **username_3**: @userLTK - you can't "build" anything in space. it's just vacuum.  obviously, as you say, each rocket payload size limits the size of that part you can send up.  if someone wanted to send up a telescope much bigger than JWT they'd send up the parts (2, 10, 100, whatever flights) and **assemble** it.   note that, hauling a factory to the moon is, of course, also obviously limited by the size of the lunar transports  
> **username_5**: You may want to read up on *adaptive optics*: https://en.wikipedia.org/wiki/Adaptive_optics  
> **username_6**: Space telescopes are **not *always*** better than Earth-based telescopes. They both have advantages and disadvantages, and whether one is "better" than another ultimately depends on the specific purpose.  

---

## 4 answers

### Answer by username_10 on 2018-06-07. Score: 8 | Accepted answer

It's very unlikely that large optical telescopes will ever be built on the Moon, because the Moon is almost the worst possible place to build them. (The surfaces any of the planets other than Earth are worse.) It has no particular advantages over orbit and costs a lot more to build there.

The Moon looked like a good location when observatory technology was film-based, because observatories required people and people needed a base to live in and work best under gravity. But we now have the technology to shade an orbiting telescope from the Sun, point it exquisitely accurately, and take endless photos without changing the film -- all in orbit. Orbit is easier to get to than the Lunar surface -- even the Webb (should it ever launch) which will be parked a million miles from Earth, is easier to get to than the surface of the moon.

If we had the space capabilities to build a giant reflector on the Moon, we could build an even bigger and better one in orbit for the same cost.

You spoke of FAST. FAST is a radio telescope. It's likewise much cheaper to build radio telescopes in orbit than on the Lunar surface. The one possible advantage of the Moon is that the far side of the Moon might have advantages of being especially radio quiet.

But even there, it seems likely that any space radio telescope would be a large array of radio telescopes joined to form a giant synthetic aperture, and that would almost certainly want to be much larger than earth-based instruments -- for which the Moon is already too small.

> **Comments:**
> **username_2**: +1 for mentioning radio telescope arrays as another example of why the Moon is unrealistic as an option.  
> **username_4**: The only thing I'm not sure I agree with is "build a better one in orbit for the same cost"   When the telescope gets big enough, the primary expense becomes the launching, not the building.   Building on the moon circumvents the launching cost.  Building on any sizable asteroid could work too, but I think some gravitation is a plus in building.  Most asteroids have close to zero gravity.  Apart from that one point, I think your answer is spot-on.  
> **username_10**: You don't build it in space in the sense of stacking up bricks and riveting pieces of steel together! A modern telescope is a *very* complex gadget and would be built in pieces by specialists on the ground using millions of man-hours and then launch with final assembly done in space.  In building a big telescope off-earth, gravity is no help at all -- it's a distinct hindrance!  
> **username_11**: For anything built on moon, the dust must be considered too. Its sharpness without weathered edges causes serious problems both to humans and machines, plus it electrostatically levitates - prone to cling to optics and everything else.  
> **username_12**: The JWST has indeed launched, and though it's very early days it seems to have deployed as well as or even better than was expected  

---

### Answer by username_7 on 2018-06-07. Score: 1

[This 2004 article](https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5487/1/Buyers-guide-to-telescopes-at-the-best-sites--Dome/10.1117/12.596320.full?SSO=1) although a little dated now, discusses the relative merits of three possible novel sites for new major optical/IR telescopes: Dome A in Antarctica, the South pole of the Moon, and the Earth-Sun L2 point (or an orbit around it). Each is best for different purposes. A particular attraction of the Lunar site is the ability to stare at the same part of the sky for very long periods to detect very faint objects.


---

### Answer by username_3 on 2018-06-06. Score: 1

Telescopes on the moon are a **fantastic idea**. If you "thought it up yourself" congratulations, because it's a great idea for the future.

As you may know we already have many fantastic telescopes in space (that is to say, generally orbiting or near our Earth). The **next step** would be telescopes on the Moon. (It is far, far, harder to build one on the moon, than simply lift one up to orbit.)

You can easily find many beginning studies about it; for example [here](https://www.space.com/5628-nasa-envisions-huge-lunar-telescope.html) is one by NASA on your great idea, from ten years ago!

Your idea is a good one, and hopefully it comes sooner rather than later. I bet we are 30 years away from telescopes on the moon. But they will come.

> **Comments:**
> **username_4**: I don't know why you'd call the Moon the "next step".  I voted you up for your NASA article though.  That pretty well covers it.  The point is that a telescope, built out of lunar material, could be larger and set up more cheaply than anything we can launch from Earth . . . in that sense, I guess it is a next step but there are several next steps already on the way, the next one is James Webb, that will unfold in space if all goes according to plan.   The real advantage to the Moon is lunar material could be used, so stuff doesn't need to be launched from Earth.  
> **username_8**: Nanotubes? In the resin mirror? Sounds silly. Why? Nanotubes, carbon fiber is more rigid than steel. Aluminium vapor deposition? On the moon? That researcher needs a 20meter mirror to be taken seriously. Better build microscopes for malians and sudanese first or you can make a ladder to the moon from them?  
> **username_1**: Building a lunar base is actually scifi, a dark side of the moon base with the industrial capacity of building high-tech telescopes is more suited to [WolrdBuilding SE](https://worldbuilding.stackexchange.com/) than [Space Exploration SE](https://space.stackexchange.com/)  

---

### Answer by username_4 on 2018-06-07. Score: 1

There are advantages and disadvantages.

Earth based telescopes have disadvantages because of the atmosphere, which blocks some light and it blocks some wavelengths almost completely and it also bends the incoming light. Some of the atmospheric displacement can be fixed with modern computers, so Earth based telescopes have improved significantly over the last 20-30 years, but they still have the disadvantage Earth's atmosphere blocking some of the light coming in from space. Today's Earth based telescopes are as good as Hubble (I read that somewhere) at least in the visible spectrum, in large part because of computerized imaging. When Hubble was launched (and fixed) at the time if was lightyears better than anything on Earth. Today it's close.

[Chandra and Spitzer](https://www.space.com/6716-major-space-telescopes.html) see in wavelengths that don't make it to Earth, so they need to be in orbit to work. James Webb will also view in the infra-red as well as visible wavelengths, so it needs to be in space to take advantage of it's infrared imaging.

Space is much better because it gets a much cleaner picture and it receives all wavelengths. There are disadvantages to being in space too, like cosmic rays, solar storms and the occasional near-light-speed proton but on average, space is better than Earth and the surface of the Moon is similar to being in space due to there being essentially no atmosphere.

A big problem with telescopes in space is that launching that much material is very expensive. It costs about $10,000 per pound to launch something into space. That's why there's so few you can count space telescopes on your fingers (fingers and toes actually, [I think there's 13](https://www.space.com/6716-major-space-telescopes.html)).

It's also important to keep large telescopes somewhat cold. ([James Webb will have a large sun shield](https://jwst.nasa.gov/sunshield.html)). That's especially important for infrared imaging. Provided the area is shaded, the moon will remain sufficiently cold.

The big advantage the Moon has is that it's full of silicon, which is what mirrors are made of, so by using lunar material, much less stuff needs to be launched and that saves a ton of money and increases the size of this theoretical telescope. That's the real advantage. We can't launch a 100 or 200 foot telescope from Earth because it's too big, but we could in theory, built one that size on the moon because there's lots and lots of stuff to use.

A smaller advantage is that the body of the moon acts as a shield for what's below it, but the real advantage is that the Moon is made of stuff that can be turned into a telescope. Really any large body a few miles in diameter would work, though working on a surface with gravity might be easier. Personally I think Ceres would be a great place to build. Very low gravity (but enough where you can set things down and not worry about them bouncing away) farther from the sun so a smaller sun-shield. Any reasonably large body in space could theoretically be used to build a telescope.

The moon, however, is closer, so it's both more easily repaired and it's close enough that it's easier to transmit images back to Earth as opposed to a Phobos based or Ceres based telescope.

This shouldn't be mistaken for easy though. It's never been done and might run into unanticipated problems and end up being quite difficult, but it's a nice idea.

> **Comments:**
> **username_8**: The silicon is full of feldspar, pure silicon on earth comes from geothermal water and sea action. Youd need hot crucibles of moon rock and refine feldspar silicon mix, un unkown industry. Youd need gold, aluminium, vapor deposition chambers, dust free clean-rooms, the moons dust is abrasive. A flintstonoscope on the moon would not be optimal use of money. After building the silicon refinery for 10billion dollars. The list of costs would exceed 200 billion in todays money... lifting machines,cranes, it would be cheaper to make homes there than big machines.  
> **username_9**: It would be insanely expensive to set up that manufacturing infrastructure just to build a telescope. Of course, if you were building a base big enough to warrant that setup, or a long-term colony, then sure you might as well build a scope at some stage.  
> **username_4**: @com.prehensible  I was going off this NASA article, which you critiqued in the other answer.    https://www.space.com/5628-nasa-envisions-huge-lunar-telescope.html   I have no idea how feasible it actually is, but I did mention that it's never been done and could be quite difficult.   Probably not something we'll see anytime remotely soon, if at all.  

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