[Europa]

Actually cameras use both lenses and mirrors and the Hubble was both a telescope and a camera.

I didn't say otherwise, did I?

It's perfectly possible to build a camera with only mirrors rather than lenses.
https://en.wikipedia.org/wiki/Catoptrics

What I said was

They don't use lenses much.
They use mirrors.

Hubble's mirror has a mass of about 800 Kg, what do you think the lenses weigh?
What's your definition of "much"?

Again the Hubble is both a camera intended to photograph the Kremlin and a telescope.  The Hubble was totally unable to focus on the the universe after being launched because it was primarily designed to read the Kremlin's mail.  What I think any of this weighs is just distracting an irrelevant

[Bored chemist]

Again the Hubble is both a camera intended to photograph the Kremlin

It does not matter how many times you say it, the claim isn't just wrong, it is impossible.
Hubble was moving too fast to get decent pictures of the Earth.
The sensors are also very wrong; they are designed for dim objects, not bright ones.

What is your purpose in coming here and being loudly wrong?

I presume you think this
https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
doesn't exist.
The mirror is about 3 times bigger than Hubble's, but it's going to be about 2000 times further from Earth, so it's about a thousand times worse as a spy satellite, and it uses Infrared which reduces the resolution even further.
It won't be able to see stuff on Earth unless it's about a hundred metres across.


Are you still saying

science was just a back seat afterthought

[Europa]

Again the Hubble is both a camera intended to photograph the Kremlin

It does not matter how many times you say it, the claim isn't just wrong, it is impossible.
Hubble was moving too fast to get decent pictures of the Earth.
The sensors are also very wrong; they are designed for dim objects, not bright ones.

What is your purpose in coming here and being loudly wrong?

I presume you think this
https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
doesn't exist.

If you presume that I read wiki you are wrong.  Now as for the Hubble being successful at it's objectives one might ask that if it were, why was no replacement ever launched.  See I never claimed that it was successful as it was a failure at launch and had to be serviced in space to be able to do anything, as far as we know anyway.  So as for how clear the classified images are of the Kremlin I can not testify too. 

[Bored chemist]

Now as for the Hubble being successful at it's objectives one might ask that if it were, why was no replacement ever launched. 

Because it was a success.
Now, decade later we have better kit so we are launching what is generally seen as the successor.

If you presume that I read wiki you are wrong. 

Pity, you might learn something.

So as for how clear the classified images are of the Kremlin I can not testify too. 

You don't need to declassify them.
The laws of physics tell you that , with a mirror that size, the best possible resolution at ground level is about 0.1 metres (and the specification says about 0.3 metres).

But. as I keep pointing out, and you keep ignoring, it's moving too fast.
All you would get is a blur.

Do you not understate that?

It's not a matter of it being a military secret; it s a matter of physical impossibility.
If you wanted a picture of the kremlin, you would do better to buy a postcard of it than to use Hubble.


Why are you posting this tosh?

[Bored chemist]

I never claimed that it was successful

No. That would be a mater of opinion anyway.
But you did claim that it did not work because it was designed as a spy camera.
However the laws of physics- the motion blurring and theoretical diffraction limited resolution-  as well as the instrumentation, make it clear that it was not.

And, since it's not a spy satellite, it wasn't designed as one (it would be a stupidly bad design) then we know it didn't fail "because" it was built as one.
So we know that there must have been a differed reason- a cock up is the most likely.

So, as I say, why are you posting conspiracy nonsense?
Did you not realise this was a science site?

[Europa]

I never claimed that it was successful

No. That would be a mater of opinion anyway.
But you did claim that it did not work because it was designed as a spy camera.
However the laws of physics- the motion blurring and theoretical diffraction limited resolution-  as well as the instrumentation, make it clear that it was not.

And, since it's not a spy satellite, it wasn't designed as one (it would be a stupidly bad design) then we know it didn't fail "because" it was built as one.
So we know that there must have been a differed reason- a cock up is the most likely.

So, as I say, why are you posting conspiracy nonsense?
Did you not realise this was a science site?

Funny how the people who designed the Hubble did not have the knowledge that you claim too have.  Which somehow fails to make any sense.  So as I said the Hubble was a 100 percent complete astronomical failure after launch as it was not intended to be a telescope, but to look into the Kremlins windows as it's primary task.  You may however be correct that this never worked properly as many things need to be tested to be confirmed failures. 

[Bored chemist]

Funny how the people who designed the Hubble did not have the knowledge that you claim too have.

What "knowledge " are you talking about?

So as I said the Hubble was a 100 percent complete astronomical failure after launch as it was not intended to be a telescope

No. It failed because they screwed up.

it was not intended to be a telescope, but to look into the Kremlins windows as it's primary task.

It could not do this.
The resolution would not be good enough, and the image would be blurred because the telescope is moving so fast.
So either they built it for this primary task, but never had a hope in hell of it doing its job, or they built it as an astronomical telescope- which (once they found a work-round for the cock-up) it did very well.

Why are you not paying attention to the simple fact that the mirror is not big enough to see details smaller than a foot or so from that altitude?

Do you understand that there is a fundamental limit to the resolution of a telescope- it was worked out a long time ago.
https://courses.lumenlearning.com/physics/chapter/27-6-limits-of-resolution-the-rayleigh-criterion/

The people at Perkin Elmer who built Hubble knew about this- partly because they weren't uneducated idiots- but mainly because they were in the business of making spy satellites.

[Europa]

Funny how the people who designed the Hubble did not have the knowledge that you claim too have.

They had the knowledge; they just screwed up a measurement.

So as I said the Hubble was a 100 percent complete astronomical failure after launch as it was not intended to be a telescope

because they screwed up.

it was not intended to be a telescope, but to look into the Kremlins windows as it's primary task.

It could not do this.
The resolution would not be good enough, and the image would be blurred because the telescope is moving so fast.
So either they built it for this primary task, but never had a hope in hell of it doing its job, or they built it as an astronomical telescope- which (once they found a work-round for the cock-up) it did very well.

Why are you not paying attention to the simple fact that the mirror is not big enough to see details smaller than a foot or so from that altitude?

Do you understand that there is a fundamental limit to the resolution of a telescope- it was worked out a long time ago.
https://courses.lumenlearning.com/physics/chapter/27-6-limits-of-resolution-the-rayleigh-criterion/

The people at Perkin Elmer who built Hubble knew about this- partly because they weren't uneducated idiots- but mainly because they were in the business of making spy satellites.

LOL now you are claiming that the faulty mirror was built on purpose.

Technically you are correct because the mirror was not imperfect when pointed at the Earth, only when facing away from the Earth, the fault was that the onboard optics could not correct for imperfect focus when pointed to the universe.

Hey secretive military stuff like this was everywhere. Again you do know that NASA was launching and servicing military satellites with the shuttle not just doing experiments with rice

[Bored chemist]

LOL now you are claiming that the faulty mirror was built on purpose.

No
I made it quite clear that they did not do it on purpose.

It failed because they screwed up.

So it looks like part of the problem here is your reading comprehension.
Do you really not understand that "screwed up" means made a mistake?

You also need to understand that a telescope primary mirror  is a telescope primary mirror . You grind the mirror to the same shape- a parabola- regardless of what you will point it at.

So, if they had made a spy satellite mirror, it would have had the same shape mirror as an astronomical telescope mirror.

But they messed it up.

[Bored chemist]

Technically you are correct because the mirror was not imperfect when pointed at the Earth, only when facing away from the Earth, the fault was that the onboard optics could not correct for imperfect focus when pointed to the universe.

If that was true (and it's impossible,by the way) ...
HOW WOULD YOU KNOW?

[Bored chemist]

You forgot toanswer a few points.

Why are you not paying attention to the simple fact that the mirror is not big enough to see details smaller than a foot or so from that altitude?

So, as I say, why are you posting conspiracy nonsense?
Did you not realise this was a science site?

But. as I keep pointing out, and you keep ignoring, it's moving too fast.
All you would get is a blur.

Do you not understand that?

Are you suggesting that Mr Gorbachev's mail was only ever in the form of advertising hoardings with letters a couple of feet high?

[Europa]

You forgot toanswer a few points.

Why are you not paying attention to the simple fact that the mirror is not big enough to see details smaller than a foot or so from that altitude?

So, as I say, why are you posting conspiracy nonsense?
Did you not realise this was a science site?

But. as I keep pointing out, and you keep ignoring, it's moving too fast.
All you would get is a blur.

Do you not understand that?

Are you suggesting that Mr Gorbachev's mail was only ever in the form of advertising hoardings with letters a couple of feet high?

My purpose is not to answer to your distraction points.  My purpose was to remind people that when launched that the Hubble space telescope was totally non functional because the mirror was ground to focus on the Earth which makes the Hubble just another spy satellite that took a few pictures of the Universe when it was not pointed at the Kremlin.

[Bored chemist]

My purpose was to remind people that when launched that the Hubble space telescope was totally non functional because the mirror was ground to focus on the Earth which makes the Hubble just another spy satellite that took a few pictures of the Universe when it was not pointed at the Kremlin.

So, you came to a science page to say something which is obviously not true because the shape you grind the mirror is the same if you point it up or down- why do you imagine it would be different?

Why would you do that?

Incidentally, pointing out that you are wrong is not a distraction; it's science.

[Europa]

My purpose was to remind people that when launched that the Hubble space telescope was totally non functional because the mirror was ground to focus on the Earth which makes the Hubble just another spy satellite that took a few pictures of the Universe when it was not pointed at the Kremlin.

So, you came to a science page to say something which is obviously not true because the shape you grind the mirror is the same if you point it up or down- why do you imagine it would be different?

Why would you do that?

Incidentally, pointing out that you are wrong is not a distraction; it's science.

Actually to focus light correctly bouncing off the near Earth as opposed to the infinity of the universe would require a slightly different parabolic curve in the mirror.  But you knew that already.

[Bored chemist]

Actually to focus light correctly bouncing off the near Earth as opposed to the infinity of the universe would require a slightly different parabolic curve in the mirror.  But you knew that already.

You seem to have read a book, but not really understood it.
The focal length of the HST is 57.6 metres.
The distance from the Earth is 540000 metres which is practically at infinity.


But you still miss the point.
If I want to change the focus of my camera from a foot away to take a picture of the Moon, I don't need to regrind the lens to a different shape.
I just move it slightly.
So. let's do the calculation.
First the easy one; how far away from the image sensor should the mirror be to take pictures at infinity- that's easy- it's the focal length

And now let's calculate how far it needs to be if we want to get a picture of the Earth (in spite on not having enough resolution, and the motion blurring making it pointless)
It's the lens formula (I know it's a mirror, but the maths is the same)
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.html
1/ o +1/i = 1/f
where f is the focal length  is the image distance and o is the object distance
OK We can rearrange that
1/o = 1/f - 1/i

f is the focal length 57.6 metres
 o is  the object distance- that's the distance to Earth  540000 metres


1/f =0.017636684
1/o = 0.000001851

so 1/i is the difference 0.017359...
and so i (the image distance) is 57.6061 metres.
So the change in focus is about 6 mm.

And they would have allowed for that variation when they built it-
Why wouldn't they?
It's not hard.
They would, of course, have to allow some focussing anyway because the focal length of the mirror (ironically) may not have been that precise.
They also needed to be able to change the focus because of requirements of different instruments within the 'scope.

So, if, as you seem to think, it was as simple focus error, they would have ben able to focus it.
No need for all the problems and embarrassment.


In particular if, as you seem to think, they wanted to be able to focus on the kremlin (it's pointless but never mind) and also on the stars, they would certainly have been able to do the same calculation I just did.


So, why are you saying they built the worlds biggest spy satellite,  disguised it as a science project (why?, by the way, the US military budget is so big that paying for Hubble wouldn't be a problem. Why not just be honest about it being a spy camera?) but they forgot that they would need to change focus?

Why do you think they were that stupid?

Your whole idea makes no sense.
If they wanted to spend that much to look at the Kremlin, they could have done a much better job- for a start you would choose a lower orbit. (or just bought a postcard.)
They didn't need to "disguise" it, they could have just kept it secret.

[Just thinking]

No the parabolic mirror is ground and polished to focus on any distance as the focus is achieved by the position of the detector. and in the case of the Hubble telescope as with most optical telescopes that is the optics are best suited to look into infinity. And infinity is according to the diameter of the mirror in relation to its resolution ability and in the case of the Hubble it is about 300 kilometres any closer than that will require some out focus.

[Just thinking]

The primary mirror of a telescope is ground and polished to a paraboloid.
It does not matter if you want to use it as a spy satellite (which is, indeed, where Perkin Elmer got their "expertise") or an astronomical telescope.


You have repeatedly shown that you do not know what you are talking about.
Why not stop wasting bandwidth?

We don't agree on much but you have this one no argument from me what a clown.

[Just thinking]

The primary mirror of a telescope is ground and polished to a paraboloid.
It does not matter if you want to use it as a spy satellite (which is, indeed, where Perkin Elmer got their "expertise") or an astronomical telescope.


You have repeatedly shown that you do not know what you are talking about.
Why not stop wasting bandwidth?

We don't agree on much but you have this one no argument from me what a clown.

Actually cameras use both lenses and mirrors and the Hubble was both a telescope and a camera.  Nothing you might have studied says any different.

Well if it didn't have a camera then they must have an astronaut up there looking throw a little eye pice.

[Europa]

Actually to focus light correctly bouncing off the near Earth as opposed to the infinity of the universe would require a slightly different parabolic curve in the mirror.  But you knew that already.

You seem to have read a book, but not really understood it.
The focal length of the HST is 57.6 metres.
The distance from the Earth is 540000 metres which is practically at infinity.


But you still miss the point.
If I want to change the focus of my camera from a foot away to take a picture of the Moon, I don't need to regrind the lens to a different shape.
I just move it slightly.
So. let's do the calculation.
First the easy one; how far away from the image sensor should the mirror be to take pictures at infinity- that's easy- it's the focal length

And now let's calculate how far it needs to be if we want to get a picture of the Earth (in spite on not having enough resolution, and the motion blurring making it pointless)
It's the lens formula (I know it's a mirror, but the maths is the same)
http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/lenseq.html
1/ o +1/i = 1/f
where f is the focal length  is the image distance and o is the object distance
OK We can rearrange that
1/o = 1/f - 1/i

f is the focal length 57.6 metres
 o is  the object distance- that's the distance to Earth  540000 metres


1/f =0.017636684
1/o = 0.000001851

so 1/i is the difference 0.017359...
and so i (the image distance) is 57.6061 metres.
So the change in focus is about 6 mm.

And they would have allowed for that variation when they built it-
Why wouldn't they?
It's not hard.
They would, of course, have to allow some focussing anyway because the focal length of the mirror (ironically) may not have been that precise.
They also needed to be able to change the focus because of requirements of different instruments within the 'scope.

So, if, as you seem to think, it was as simple focus error, they would have ben able to focus it.
No need for all the problems and embarrassment.


In particular if, as you seem to think, they wanted to be able to focus on the kremlin (it's pointless but never mind) and also on the stars, they would certainly have been able to do the same calculation I just did.


So, why are you saying they built the worlds biggest spy satellite,  disguised it as a science project (why?, by the way, the US military budget is so big that paying for Hubble wouldn't be a problem. Why not just be honest about it being a spy camera?) but they forgot that they would need to change focus?

Why do you think they were that stupid?

Your whole idea makes no sense.
If they wanted to spend that much to look at the Kremlin, they could have done a much better job- for a start you would choose a lower orbit. (or just bought a postcard.)
They didn't need to "disguise" it, they could have just kept it secret.

The distance from the Hubbles orbit to Earth is not infinity when referencing telescopes that are typically set up to view infinity as one would have when viewing the universe.  This is why the mirror was flawed, it's a fact as it happened because when the spy satellite disguised as a telescope was launched it WAS NOT A FUNCTIONING TELESCOPE.  Not sure why anyone would argue this as nothing that the government produces is what it says it is, remember when Hughes was mining manganese and really lifting a Soviet sub? Actually giving this camera a dual use made it more functional in the long run, but it did take photos of the Earth, with the highest resolution ever I do believe.

[alancalverd]

There are plenty of purely military satellites out there. Everybody knows that. The strength of Hubble is its light-gathering capacity, not its spatial resolution. If you want to spy on anyone on earth you really need a stereo camera in low orbit, and there's plenty of ambient light. And if you want to modify a military satellite, you don't publish your calculations, use a civilian crew, and do it on live public television.

Anyway, consider this as a warning: unsupported conspiracy theories are not really welcome here.