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Re: Null corrector for a fast mirror

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  • paul valleli
    John, Last fall, I simulated a point source offset from the OA of a spherical mirror to determine the amount of astigmatism at the offest knife edge of the
    Message 1 of 36 , May 10, 2013
      John,
      Last fall, I simulated a point source offset from the OA of a spherical mirror to determine the amount of astigmatism at the offest knife edge of the classic Foucault Test.
      There was a divergence angle in radians that I put in the setup parameters.
      I would have to look it up. It required a coordinate break at the mirror.
      I'll look it up if you wish.
      PaulĀ 
    • John
      For a complete solution source anywhere I think the sag at h is needed which can probably be derived from that link. :-) Not sketched anything out so a pure
      Message 36 of 36 , May 13, 2013
        For a complete solution source anywhere I think the sag at h is needed which can probably be derived from that link. :-) Not sketched anything out so a pure guess. From memory Sixtests allows the mirror to source distance to be specified but that may be just to reduce errors from normal Foucault readings. I don't think it allows offsets to be specified which are another source of error apart from any aberration effects.

        Where some views of aberrations go astray is that when a mask is used the aberrations of the whole mirror may not be important. Instead it's the size of the circles of confusion produced by a series of small off axis mirrors in relationship to their diffraction disc size.

        I also suspect that there is another test that could be used these days but no sums done to check how large a sensor is needed for good say 1/20 wave results. Hartman, if that is how it's spelled. That one would just involve taking an exposure with the lens off a dslr, moving it a specific distance along the axis of the mirror and taking another.

        John
        -
        --- In atm_free@yahoogroups.com, "Richard F.L.R. Snashall" <rflrs@...> wrote:
        >
        > On 5/12/2013 6:06 PM, John wrote:
        > > So what is the equation for the exact slope of a conic versus height?
        >
        > Cf:
        >
        > http://www.atmlist.net/contrib/rflrs-at-verizon-dot-net/rflrs/conics.htm
        >
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