ATM self contained vibration damper....

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

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



_________________________________________________________________
Join the world’s largest e-mail service with MSN Hotmail. 
http://www.hotmail.com