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Quote from: Europa on 19/07/2021 18:43:04Actually 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/CatoptricsWhat I said was Quote from: Bored chemist on 19/07/2021 18:37:23They 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"?
Actually cameras use both lenses and mirrors and the Hubble was both a telescope and a camera.
They don't use lenses much.They use mirrors.
Again the Hubble is both a camera intended to photograph the Kremlin
science was just a back seat afterthought
Quote from: Europa on 19/07/2021 19:04:12Again the Hubble is both a camera intended to photograph the KremlinIt 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_Telescopedoesn't exist.
Now as for the Hubble being successful at it's objectives one might ask that if it were, why was no replacement ever launched.
If you presume that I read wiki you are wrong.
So as for how clear the classified images are of the Kremlin I can not testify too.
I never claimed that it was successful
Quote from: Europa on 19/07/2021 19:20:25I 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.
So as I said the Hubble was a 100 percent complete astronomical failure after launch as it was not intended to be a telescope
it was not intended to be a telescope, but to look into the Kremlins windows as it's primary task.
Quote from: Europa on 19/07/2021 20:08:12Funny 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.Quote from: Europa on 19/07/2021 20:08:12So as I said the Hubble was a 100 percent complete astronomical failure after launch as it was not intended to be a telescopebecause they screwed up.Quote from: Europa on 19/07/2021 20:08:12 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.
It failed because they screwed up.
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.
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?
You forgot toanswer a few points.Quote from: Bored chemist on 19/07/2021 20:24:10Why 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?Quote from: Bored chemist on 19/07/2021 19:56:59So, as I say, why are you posting conspiracy nonsense?Did you not realise this was a science site?Quote from: Bored chemist on 19/07/2021 19:52:33But. 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?Quote from: Bored chemist on 19/07/2021 18:04:50Are 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 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.
Quote from: Europa on 19/07/2021 20:50:52My 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.
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?
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.
Quote from: Europa on 19/07/2021 21:12:01Actually 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 lengthAnd 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.html1/ o +1/i = 1/fwhere f is the focal length is the image distance and o is the object distanceOK We can rearrange that 1/o = 1/f - 1/if is the focal length 57.6 metres o is the object distance- that's the distance to Earth 540000 metres1/f =0.0176366841/o = 0.000001851so 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.