Re: Perfect lens

Discussion in 'Digital Photography' started by James Silverton, Apr 2, 2013.

  1. On 4/2/2013 4:08 AM, Alfred Molon wrote:
    > Just wondering, if money played no role how good could lenses be?
    >
    > No chromatic aberrations, no geometric distortions, huge sharpness from
    > corner to corner even wide open, or are there some physical constraints
    > which prevent from producing a perfect lens?
    >

    It only took $60 million to reconfigure the wrongly designed Hubble
    Scope and the results have been wonderful.

    --
    Jim Silverton (Potomac, MD)

    Extraneous "not" in Reply To.
     
    James Silverton, Apr 2, 2013
    #1
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  2. James Silverton

    RichA Guest

    On Apr 2, 3:15 pm, Alan Browne <>
    wrote:
    > On 2013.04.01 22:20 , James Silverton wrote:
    >
    > > On 4/2/2013 4:08 AM, Alfred Molon wrote:
    > >> Just wondering, if money played no role how good could lenses be?

    >
    > >> No chromatic aberrations, no geometric distortions, huge sharpness from
    > >> corner to corner even wide open, or are there some physical constraints
    > >> which prevent from producing a perfect lens?

    >
    > > It only took $60 million to reconfigure the wrongly designed Hubble
    > > Scope and the results have been wonderful.

    >
    > Had it been done correctly the first time the results would have been
    > wonderfuller and sooner.
    >


    Meanwhile, apparently, a perfect mirror sat back at Earth, not having
    been used. I don't know what they ever did with it.
     
    RichA, Apr 2, 2013
    #2
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  3. James Silverton

    DanP Guest

    On Tuesday, April 2, 2013 10:07:38 PM UTC+1, RichA wrote:

    > Meanwhile, apparently, a perfect mirror sat back at Earth, not having
    > been used. I don't know what they ever did with it.


    The story I know is 2 were made. After the images were looked at and fond unusable the second mirror was analyzed and found faulty. The problem was traced to a spec of paint coming off in the jig used to make the 2 mirrors. That distorted the light used to analyse the polished surface.

    The second mirror being made in the same way made it possible to understandthe fault and construct optics to correct the one in space.


    DanP
     
    DanP, Apr 3, 2013
    #3
  4. James Silverton

    RichA Guest

    On Apr 2, 7:25 pm, DanP <> wrote:
    > On Tuesday, April 2, 2013 10:07:38 PM UTC+1, RichA wrote:
    > > Meanwhile, apparently, a perfect mirror sat back at Earth, not having
    > > been used.  I don't know what they ever did with it.

    >
    > The story I know is 2 were made. After the images were looked at and fondunusable the second mirror was analyzed and found faulty. The problem was traced to a spec of paint coming off in the jig used to make the 2 mirrors.That distorted the light used to analyse the polished surface.
    >
    > The second mirror being made in the same way made it possible to understand the fault and construct optics to correct the one in space.
    >
    > DanP


    That's so far-fetched it reminds me of the movie, "Andromeda Strain"
    where a tiny strip of paper prevents a bell in a machine from ringing,
    preventing any messages from reaching the microbe-hunter team and
    inadvertently preventing an atomic blast that would have mutated the
    virus to be a world-wide scourge.. Still, stranger things have
    happened.
     
    RichA, Apr 3, 2013
    #4
  5. James Silverton

    Martin Brown Guest

    On 03/04/2013 00:25, DanP wrote:
    > On Tuesday, April 2, 2013 10:07:38 PM UTC+1, RichA wrote:
    >
    >> Meanwhile, apparently, a perfect mirror sat back at Earth, not having
    >> been used. I don't know what they ever did with it.

    >
    > The story I know is 2 were made. After the images were looked at and fond unusable the second mirror was analyzed and found faulty. The problem was traced to a spec of paint coming off in the jig used to make the 2 mirrors. That distorted the light used to analyse the polished surface.


    Absolutely untrue. The Kodak mirror was independently manufactured and
    entirely correct in its optical implementation. It wasn't quite as
    finely polished but it would have worked if it had been selected to fly.
    They were obsessed with "smoothness" of polish at the time.

    The fault lay inside P-E and their arrogant management practices as is
    made clear in this article on the inside story.

    http://people.tamu.edu/~v-buenger/658/Hubble.pdf

    Low ball bidding to get the contract was at the root of why P-E and NASA
    were cutting corners and ignoring inconvenient test results. They had
    way too much faith in the fancy null-tester and didn't want to hear
    anything adverse or do tests that might cost money off the bottom line.

    Kodak's higher bid for the whole project had included a full system test
    on the ground - which would have found the fault (which they actually
    didn't make). It was ironic that P-E skipped full system test and then
    due to the shuttle disaster the scope didn't fly for several years.
    During that time its space flight qualified cameras were largely
    overtaken in sensitivity by the rapidly advancing CCD technology.

    > The second mirror being made in the same way made it possible to understand the fault and construct optics to correct the one in space.


    Not true. The second mirror made by Kodak using its own proprietary and
    allegedly inferior test techniques was figured correctly but not quite
    as perfectly smooth polished as the Perkin-Elmer mirror that flew.

    The error was in the P-E null corrector test jig and they placed far too
    much faith in its results when the error was so gross that even basic
    amateur mirror makers sanity checks would have found the fault!

    The fault was understood by a radio astronomy computational holography
    technique for figuring large telescope dishes pioneered by Jodrell Bank
    for adjusting the panels on their big dish. It was tweaked to work at
    optical wavelengths and used to determine the figure of the HST from a
    series of star test images taken at a range of positions and either side
    of true "focus". Unfortunately NASA's servers are offline at present so
    I cannot point you to chapter and verse.

    --
    Regards,
    Martin Brown
     
    Martin Brown, Apr 3, 2013
    #5
  6. James Silverton

    Robert Coe Guest

    On Tue, 02 Apr 2013 16:15:58 -0400, Alan Browne
    <> wrote:
    : On 2013.04.01 22:20 , James Silverton wrote:
    : > On 4/2/2013 4:08 AM, Alfred Molon wrote:
    : >> Just wondering, if money played no role how good could lenses be?
    : >>
    : >> No chromatic aberrations, no geometric distortions, huge sharpness from
    : >> corner to corner even wide open, or are there some physical constraints
    : >> which prevent from producing a perfect lens?
    : >>
    : > It only took $60 million to reconfigure the wrongly designed Hubble
    : > Scope and the results have been wonderful.
    :
    : Had it been done correctly the first time the results would have been
    : wonderfuller and sooner.

    In a larger sense, it was done right the first time, in that the designers
    anticipated that changes and repairs might have to be made over the life of
    the device. The possibility of making serious repairs in space was a novelty
    at the time.

    Bob
     
    Robert Coe, Apr 6, 2013
    #6
  7. On Apr 6, 10:18 am, Robert Coe <> wrote:

    >
    > In a larger sense, it was done right the first time, in that the designers
    > anticipated that changes and repairs might have to be made over the life of
    > the device. The possibility of making serious repairs in space was a novelty
    > at the time.
    >
    > Bob


    No, it wasn't done perfectly the first time. Due to a measurement
    error the primary mirror surface was in error.

    http://www.richardfisher.com
     
    Helpful person, Apr 16, 2013
    #7
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