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Stars focusing into lines

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  • Robert
    I need some help in figuring out a problem I am having getting a new camera setup in my scope. I am using an 8 reflector that is 1000mm with a DSI III pro. I
    Message 1 of 4 , May 1, 2008
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      I need some help in figuring out a problem I am having getting a new
      camera setup in my scope. I am using an 8" reflector that is 1000mm
      with a DSI III pro.

      I have the DSI attached to a CFW8a filter wheel and use a MPCC coma
      corrector in the nosepiece.

      With this setup I get stars that look like little lines when it is
      just outside of focus. Images are producing stars that are very
      elongated.

      I can rule out guiding as a problem. I have used this my same scope
      setup and mount with a different camera and no guiding issues. The
      star problem shows up in images as fast as .2 seconds.

      I can also rule out colimation. The scope is well colimated and my
      DSLR in the same scope produces perfect stars.

      One thing I notice is when I check the focus on a bright star the
      diffraction spikes on one side dont converge. Normally when I get
      perfect focus all 4 spikes are perfect lines. With this camera setup
      I get 2 spikes as nice lines and 2 spikes split and blurred.

      Ok so now where do I look for the issue? My thought is this is some
      kind of tilt problem and I was wondering if the symptons match that
      assumption.

      My next step was to remove the CFW8 from the mix and try the camera
      straight through and if the problem lies with the camera itself.

      Any tips or tricks that might help me figure this one out?

      Thanks


      Robert
    • sforster12
      It sounds like a sagging issue. I had this with a Tak scope even with all screw together connectors until I adjusted the focuser. STU ... new ... setup
      Message 2 of 4 , May 1, 2008
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        It sounds like a sagging issue. I had this with a Tak scope even with
        all screw together connectors until I adjusted the focuser.

        STU

        -- In ccd-newastro@yahoogroups.com, "Robert" <robt2112@...> wrote:
        >
        > I need some help in figuring out a problem I am having getting a
        new
        > camera setup in my scope. I am using an 8" reflector that is 1000mm
        > with a DSI III pro.
        >
        > I have the DSI attached to a CFW8a filter wheel and use a MPCC coma
        > corrector in the nosepiece.
        >
        > With this setup I get stars that look like little lines when it is
        > just outside of focus. Images are producing stars that are very
        > elongated.
        >
        > I can rule out guiding as a problem. I have used this my same scope
        > setup and mount with a different camera and no guiding issues. The
        > star problem shows up in images as fast as .2 seconds.
        >
        > I can also rule out colimation. The scope is well colimated and my
        > DSLR in the same scope produces perfect stars.
        >
        > One thing I notice is when I check the focus on a bright star the
        > diffraction spikes on one side dont converge. Normally when I get
        > perfect focus all 4 spikes are perfect lines. With this camera
        setup
        > I get 2 spikes as nice lines and 2 spikes split and blurred.
        >
        > Ok so now where do I look for the issue? My thought is this is some
        > kind of tilt problem and I was wondering if the symptons match that
        > assumption.
        >
        > My next step was to remove the CFW8 from the mix and try the camera
        > straight through and if the problem lies with the camera itself.
        >
        > Any tips or tricks that might help me figure this one out?
        >
        > Thanks
        >
        >
        > Robert
        >
      • Robert
        yeah that might be an issue. This camera setup is heavier than the DSLR. I will take a close look at the focuser and see if that is a problem. Robert ... with
        Message 3 of 4 , May 1, 2008
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          yeah that might be an issue. This camera setup is heavier than the
          DSLR. I will take a close look at the focuser and see if that is a
          problem.

          Robert

          --- In ccd-newastro@yahoogroups.com, "sforster12" <SHFORSTER1@...>
          wrote:
          >
          > It sounds like a sagging issue. I had this with a Tak scope even
          with
          > all screw together connectors until I adjusted the focuser.
          >
          > STU
          >
          > -- In ccd-newastro@yahoogroups.com, "Robert" <robt2112@> wrote:
          > >
          > > I need some help in figuring out a problem I am having getting a
          > new
          > > camera setup in my scope. I am using an 8" reflector that is
          1000mm
          > > with a DSI III pro.
          > >
          > > I have the DSI attached to a CFW8a filter wheel and use a MPCC
          coma
          > > corrector in the nosepiece.
          > >
          > > With this setup I get stars that look like little lines when it
          is
          > > just outside of focus. Images are producing stars that are very
          > > elongated.
          > >
          > > I can rule out guiding as a problem. I have used this my same
          scope
          > > setup and mount with a different camera and no guiding issues.
          The
          > > star problem shows up in images as fast as .2 seconds.
          > >
          > > I can also rule out colimation. The scope is well colimated and
          my
          > > DSLR in the same scope produces perfect stars.
          > >
          > > One thing I notice is when I check the focus on a bright star the
          > > diffraction spikes on one side dont converge. Normally when I get
          > > perfect focus all 4 spikes are perfect lines. With this camera
          > setup
          > > I get 2 spikes as nice lines and 2 spikes split and blurred.
          > >
          > > Ok so now where do I look for the issue? My thought is this is
          some
          > > kind of tilt problem and I was wondering if the symptons match
          that
          > > assumption.
          > >
          > > My next step was to remove the CFW8 from the mix and try the
          camera
          > > straight through and if the problem lies with the camera itself.
          > >
          > > Any tips or tricks that might help me figure this one out?
          > >
          > > Thanks
          > >
          > >
          > > Robert
          > >
          >
        • phils67
          You might try unscrewing the MPCC 1/4 turn and seeing if the diffraction effect moves to the other set of vanes. If it does, then I d suspect something related
          Message 4 of 4 , May 5, 2008
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            You might try unscrewing the MPCC 1/4 turn and seeing if the
            diffraction effect moves to the other set of vanes. If it does, then
            I'd suspect something related to the MPCC.

            Phil Sherman


            --- In ccd-newastro@yahoogroups.com, "Robert" <robt2112@...> wrote:
            >
            > I need some help in figuring out a problem I am having getting a new
            > camera setup in my scope. I am using an 8" reflector that is 1000mm
            > with a DSI III pro.
            >
            > I have the DSI attached to a CFW8a filter wheel and use a MPCC coma
            > corrector in the nosepiece.
            >
            > With this setup I get stars that look like little lines when it is
            > just outside of focus. Images are producing stars that are very
            > elongated.
            >
            > I can rule out guiding as a problem. I have used this my same scope
            > setup and mount with a different camera and no guiding issues. The
            > star problem shows up in images as fast as .2 seconds.
            >
            > I can also rule out colimation. The scope is well colimated and my
            > DSLR in the same scope produces perfect stars.
            >
            > One thing I notice is when I check the focus on a bright star the
            > diffraction spikes on one side dont converge. Normally when I get
            > perfect focus all 4 spikes are perfect lines. With this camera setup
            > I get 2 spikes as nice lines and 2 spikes split and blurred.
            >
            > Ok so now where do I look for the issue? My thought is this is some
            > kind of tilt problem and I was wondering if the symptons match that
            > assumption.
            >
            > My next step was to remove the CFW8 from the mix and try the camera
            > straight through and if the problem lies with the camera itself.
            >
            > Any tips or tricks that might help me figure this one out?
            >
            > Thanks
            >
            >
            > Robert
            >
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