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Eyepiece question

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  • Steve
    I m a relative newbie and just buying my first eyepieces for a 16 dob I m building. I received in the mail today a 6mm lens (not for the dob, but for a 120mm
    Message 1 of 6 , Jul 31, 2009
      I'm a relative newbie and just buying my first eyepieces for a 16" dob
      I'm building. I received in the mail today a 6mm lens (not for the dob,
      but for a 120mm refractor I bought used) that I bought used from
      Astromart. It is a Smart Astronomy SA Long Eye relief lens with about
      55 degree field of view. To look at it, it appears to have never been
      used. But, when I hold it up and look thru it toward the light, I see
      what appear to be 'flaws' in the glass. I've cleaned the glass outside
      and made sure there is nothing like dust on the outside. My question:
      is it 'normal' to see flaws in optical glass that appear like flaws in a
      diamond or something? They appears as dark steaks, more or less.

      --
      "Where the people fear the government, you have tyranny; where the government fears the people, you have liberty." - Thomas Jefferson
    • Jack & Lynn Kramer
      From: Steve ... Simple answer, Steve - no, it s not normal to see flaws such as you describe. Even an old eyepiece should not have marks
      Message 2 of 6 , Aug 1, 2009
        From: "Steve" <svanos2@...>
        > is it 'normal' to see flaws in optical glass that appear like flaws in a
        > diamond or something? They appears as dark steaks, more or less.

        Simple answer, Steve - no, it's not normal to see flaws such as you
        describe. Even an old eyepiece should not have marks that appear between the
        lenses, although it's possible for the exteriors of the eye lens and field
        lens to develop minute scratches from too aggresive cleaning.

        Jack Kramer
        Lily Lake, Illinois
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