Re: ATM self contained vibration damper....

["benoit schillings" <benoit_schillings@hotmail.com>]

yes, I'm well familiar with wind screens ! The thing is that
in order to really efficiently block the wind for a scope
like mine, the wind screen has to be really big and difficult
to setup... obvious limits there.

Now on the issue that the vibration damper needs to be coupled
with something else not moving, tuned massed dampers can certainly
damp vibrations without that constrains for a "narrow" band of
frequency... the key is to know if one can make a broader band
damper (particule dampers ?)

-- benoit


>From: "Jim Miller" <jim@jtmiller.com>
>Reply-To: "Jim Miller" <jim@jtmiller.com>
>To: "benoit schillings" <benoit_schillings@hotmail.com>,<atm@shore.net>
>Subject: Re: ATM self contained vibration damper....
>Date: Tue, 27 Aug 2002 13:04:10 -0700
>
>vibration dampers operate by using motion to create heat (usually). this
>means the moving part has to move and be coupled in a lossy fashion to
>something not moving in the same direction.
>
>is there no way to put the scope in the lee of some object which can 
>deflect
>the wind? if you are doing ccd rather than visual work can you lower the
>tripod to the lowest possible height and then erect a screen upwind?
>
>jtm
>
>----- Original Message -----
>From: "benoit schillings" <benoit_schillings@hotmail.com>
>To: <atm@shore.net>
>Sent: Tuesday, August 27, 2002 12:07 PM
>Subject: ATM self contained vibration damper....
>
>
>
>One the major limitation I find when doing ccd imaging is that
>in most cases, when imaging from the top of a mountain good seeing
>is generally corelated with medium strength wind which of course
>has a tendency (even with my semi-heavy scope) to counter the advantage
>of good seeing.
>I use my AO-7, but in many cases, the dominant vibration of the
>instrument will be around 5 to 10 Hz which is hopeless to correct
>with a tip-tilt mirror unless I was able to correct at 100 Hz or
>so, something which is not common by virtue of lacks of bright guide
>stars.
>
>I started thinking a while back at some lower tech way to dissipate
>this high frequency vibration from my scope by using a long shock
>absorber attached to the top end of the scope and connecting to the
>ground somewhere around the scope, but decided that this was way too
>much pain to be practical, it would also likely have a prefered
>direction for the vibration reduction, something which is not always
>doable of sufficient.
>
>I remember seing in an old s&t of the idea of having a chain attached
>from the top of the scope and hanging into a bucked of oil... other
>that the fact that this is yet again a difficult setup, this would
>not work well if the scope is pointed toward the zenith... so I am
>now wondering if one could build a self enclosed system which would
>act in the same way but could just be attached to the top of the instrument
>and dissipate some of that vibration energy.
>
>some of the q&d ideas I was thinking about was a cylinder partly filled
>with oil, or maybe filled with two liquids which would not mixed...
>another idea would be to have a mass held by 4 springs that would
>be semi-tuned to the natural vibration of the scope, but I'm finding
>myself out of my depth & area when it comes to what would and what
>wouldn't work.
>
>Does anybody on the list has some idea of the subject, or better
>experimented in that field ? It seems to me that the same problem
>must exist for large dobs, and finding an easy way to kill a good
>deal of these vibrations would allow us all to build lightweight scopes
>which would be more resilient to wind & other vibration sources.
>
>
>-- Benoit
>
>
>
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