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Re: [ccd-newastro] Question about flat's positional angle

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  • Yahoo - Wodaski
    The dust motes that cause those shadows are usually either on the camera itself, or on the filter wheel. For most setups, rotation will rotate both, so the
    Message 1 of 3 , Jun 30, 2007
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      The dust motes that cause those shadows are usually either on the camera
      itself, or on the filter wheel. For most setups, rotation will rotate
      both, so the dust motes will not change due to rotation.

      What may - or may not - change with rotation is the overall illumination
      of the frame. If something is off-center, rotating the camera could
      result in flats that are subtly (or glaringly) different. The only way
      to know for sure is to try it and see if the flats works after rotation.

      Ron W

      wenjehpeng wrote:
      > Hi,
      > This is another newbie¡¦s question about flat.
      > Suppose I made a T-Shirt flat with ST2000XM at positional angle of 270.
      > Can this flat be applied to images when ST2000Xm were rotated at
      > different angles? It seemed like dust motes will change position when
      > camera is rotated. If this is true, should I take flat with different
      > positional angles ?
      > Sincerely,
      > wenjehpeng
      >
      >
      >
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
    • wenjehpeng
      ... camera itself, or on the filter wheel. For most setups, rotation will rotate both, so the dust motes will not change due to rotation. What may - or may
      Message 2 of 3 , Jun 30, 2007
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        --- In ccd-newastro@yahoogroups.com, Yahoo - Wodaski <yahoo@...> wrote:
        > The dust motes that cause those shadows are usually either on the
        camera itself, or on the filter wheel. For most setups, rotation will
        rotate both, so the dust motes will not change due to rotation.
        What may - or may not - change with rotation is the overall
        illumination of the frame. If something is off-center, rotating the
        camera could result in flats that are subtly (or glaringly) different.
        The only way to know for sure is to try it and see if the flats works
        after rotation.
        >
        > Ron W

        You are always so kind to newbie's question. Thank you.
        sincerely,
        wenjehpeng
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