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29058Re: Best Drive System For Dob

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  • David
    Jul 1, 2004
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      Ron,

      Thank you for your thoughtful reply. I am new to the group and
      did not expect to hear from you. Your book is what changed my
      curiosity in CCD work into ambition.

      I had a feeling that the dual axis equatorial platform would be
      the way to go. Some of the other posts here offer ways to do that
      with cost in mind.

      As for the truss, I am trying to navigate the trade-offs between
      stiffness and wind resistance. I am concerned that an 8 pole truss
      system will catch too much wind, defeating the goal of stability. I
      am considering using two oversized truss poles with cross supports.

      Thank you again for your post.

      -David

      --- In ccd-newastro@yahoogroups.com, "Wodaski Yahoo" <yahoo@n...>
      wrote:
      > It is easier to build a robust, accurate, and precise equatorial
      platform
      > than it is to do the same with an instrument rotator. Some reasons:
      >
      > * You can't just build an instrument rotator to high quality if you
      go that
      > route; you still need a high-quality drive and tracking mechanism
      anyway to
      > smooth out the bumps. So you really have to build two high-quality
      > high-precision systems if you go this route. And you are also
      tracking in
      > two axes at all times.
      >
      > * There are a number of off-the-shelf aluminum equatorial tracking
      platforms
      > for Dobs that will track very well for imaging. And if you build it
      > yourself, you only have to make one precision system. And an EQ
      platform
      > tracks in only one axis.
      >
      > For either case, you are going to need a stiff truss system to
      support the
      > secondary cage and the CCD camera. It needs to be stiffer than if
      it were
      > just for visual use both to maintain collimation as you slew, and
      to reduce
      > vibration during imaging.
      >
      > This is not to say that you couldn't do a nice derotator-based
      system, but
      > it will be harder to pull off well.
      >
      >
      > Ron Wodaski
      > The New CCD Astronomy
      > http://www.newastro.com/ipb
      >
      > -----Original Message-----
      > From: David [mailto:dwasch@c...]
      > Sent: Wednesday, June 30, 2004 5:08 PM
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