Digital to Match film…

  • Posted: 16 February 2002 09:08 PM #31

    On 2002-02-16 11:56, tbone1 wrote:

    ... Just imagine if they’d actually ground the mirror right and didn’t have all the loss from the extra optical elements they had made to correct for the bad mirror.

    Correct me if i’m wrong here but didn’t the company who ground Hubble’s mirror do the most exact job in mirror grinding history? From what I’ve read, they ground the mirror exactly to the specs they were given. The wrong specifications.
    The article said that they ground it during nighttime hours because of ground vibrations from an interstate a few MILES away!

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    <font size=-1>[ This Message was edited by: Photodan on 2002-02-17 01:09 ]</font>


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  • Posted: 17 February 2002 09:11 AM #32

    Yes, Perkin-Elmer (which was bought by Hughes, which is now Raytehon ... everyone follow that?) did one heck of a job, but with the wrong specs. I think the mirror, and the edge of the 96” mirror, is within 1/100th of a wavelength of visible light.

    The most impressive mirrors, however, are those for x-ray telescopes. Generally, your mirror has to be accurate to within 1/10th of a wavelength, and x-rays have a very small wavelength. Also, you can’t just use a standard mirror, because an x-ray will pass through the surface. However, you can use a low-angle-of-incidence setup so that, turned on its side, the mirror gently deflects the x-ray photon to the detector. There is no margin for error in the mirror or the assembly. To be honest, I’m amazed anyone ever figured out a way to get a working x-ray telescope into orbit.



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