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Re: [ccd-newastro] Measuring stability

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  • James
    Very good advice below. And be aware that your roof will likely be radiating heat during the first part of the night. It might be helpful to locate your
    Message 1 of 6 , Mar 9, 2013
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      Very good advice below. And be aware that your roof will likely be radiating heat during the first part of the night. It might be helpful to locate your equipment near one edge (probably southern) so that you look through air not radiating heat upward from the roof at least some of the time. If you put a tripod on the roof you can make vibration dampeners for the tripod feet using a product called sorbothane. (I did some solar viewing from a loft floor - my home made sorbothane feet dampened vibration about 80%.)

      Another easy test is to use a bowl with water in it. Put it on the roof and walk around it. See if you get ripples on the surface of the water. I'm sure you know that almost any vibration is a killer for ap.

      James in AZ

      Sent from my iPhone

      On Mar 9, 2013, at 12:57 PM, Ron Wodaski <yahoo@...> wrote:

      > It's unlikely that you will be able to mount a telescope to any part of the house itself and get sufficient isolation for imaging.
      >
      > But if you want to measure, the surest, and simplest test i can come up with is to put something up there without about the same weight and lever arm as your mount + scope, and then put a laser on top of that. Jump up and down (and maybe try to mimic wind pressure with your hands) - you can use some basic trig to determine the arcseconds (or worse) of movement of the laser on another house, a tree, a fence, the ground, whatever you can aim at.
      >
      > The other thing to consider are vibrations from equipment in the house - a washing machine, for example, but everything from a sink disposal to anyone (including you) walking anywhere in the house would get transmitted, since the house and the telescope are in direct contact with each other.
      >
      > The 'correct' way to do this, BTW, is to cut a hole in the roof, attach a long pier to the ground, and then build a dome on top of the roof. That way, the pier and telescope are isolated from all the vibrations and resonances of the house.
      >
      > Ron Wodaski
      >
      > On Mar 9, 2013, at 11:34 AM, Mark Striebeck <mark.striebeck@...> wrote:
      >
      > > Hi,
      > >
      > > Sorry, this is a little bit off topic, but I hope that some folks have some
      > > experience in this area.
      > >
      > > I'm toying with the idea of mounting my scope on top of our house. We have
      > > an eichler house, I.e. flat roof (good) but it's also made mostly of wood.
      > > My concern is that the roof is not stable enough for astrophotography.
      > >
      > > What's the best/easiest way to find out. I would love to avoid carrying all
      > > my gear up there. We don't have easy access (just a ladder).
      > >
      > > I thought about getting a small seismograph or such and mount it there and
      > > see what it does. But I would need some baseline to interpret the result.
      > >
      > > Thanks for any ideas.
      > >
      > > MarkS
      > >
      > >
      > > [Non-text portions of this message have been removed]
      > >
      > >
      > >
      > > ------------------------------------
      > >
      > >
      > >
      > >
      >
      >


      [Non-text portions of this message have been removed]
    • Mike Dodd
      ... I agree with Ron -- it s doubtful the wooden roof will be solid enough for astro imaging. You could mount a laser pointer on a tripod and aim it at a white
      Message 2 of 6 , Mar 9, 2013
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        Mark Striebeck wrote:
        > My concern is that the roof is not stable enough for astrophotography.
        >
        > What's the best/easiest way to find out.

        I agree with Ron -- it's doubtful the wooden roof will be solid enough
        for astro imaging.

        You could mount a laser pointer on a tripod and aim it at a white target
        20-30 feet away. Tape the power button "on" and mark the spot on the
        target. Have a helper stand near the target watching the spot. Walk
        around near the tripod and ask the helper to mark any variations of the
        laser spot from the original position.

        If it moves, your roof isn't rigid enough.
        --
        Mike

        Mike Dodd
        http://astronomy.mdodd.com
        Louisa County, Virginia USA N37.58.23 W77.56.24
      • Stan
        ... The problem with these schemes is that they don t easily quantify the amplitude of the vibrations. If the imaging is wide-field / low-res then it can
        Message 3 of 6 , Mar 9, 2013
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          --- Mike Dodd <mike@...> wrote:
          > mount a laser pointer...

          The problem with these schemes is that they don't easily quantify the amplitude of the vibrations. If the imaging is wide-field / low-res then it can tolerate some vibration.

          I think the most definitive test is to haul the actual gear up there and see what happens. Don't be lazy! <g>

          Stan
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