Re: ATM self contained vibration damper....

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

funny or not ;-) I did consider making a hole for the scope... just
that this is a lot of work with all the rock & stones... I would
need some explosive to do it fast !

-- 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 13:44:56 -0700
>
>i'm somewhat familiar with mass dampers from some work with gyroscopes. 
>mass
>dampers basically use a mass which is unlikely to move with the input
>provided coupled to the object of interest. for a scope this would need to
>be large and coupled in two axes presumably to the eyepiece end for
>structural reasons.
>
>how about digging a hole? (only slightly facetiously...)
>
>jtm
>
>----- Original Message -----
>From: "benoit schillings" <benoit_schillings@hotmail.com>
>To: <jim@jtmiller.com>; <atm@shore.net>
>Sent: Tuesday, August 27, 2002 1:22 PM
>Subject: Re: ATM self contained vibration damper....
>
>
>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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