A question about vibration

I would like to get some opinions on vibration dampening on a 10" f/6 structure.
Is it common to get a bit of vibration and a dampening time of 1.5-2 secounds on a longer small aperture scope of this type?
Is it because of the long truss tubes in relation to the size of the structure?
Does the light wieght increase this tendency?
What can be done to lessen this vibration?

H[COLOR="Purple"]i Floyd!
I have a 10" f/6 "Alice" clone; two tube alt/az truss style scope. It does indeed take a little time to dampen after being moved. I made it to have a very portable scope so light weight was a factor when I built it. I'm sure this leads to some of the dampening slowness but I've learned to live with it by being smooth and deliberate with motions...slow, deliberate release of the focuser board after a move is second nature to me.

I agree about the size of the truss tubes. In my case with only two, they have to be pretty stiff. The first set I used allowed too much deflection and the dampening time was pretty long. Bigger tubing really helped.

I think the light weight also adds to the dampening problem. In my case, I don't want extra weight so I have learned to live with what I have.

Are you using your 10" on an tracking platform? I tried my 10" on the large tracking platform I have and the dampening problem was much worse. Again, I can deal with it but it seems to make using the scope less enjoyable, even though I love tracking, so I usually use the scope firmly on terra firma.

I've read about some novel ideas to lessen vibration...expanding foam in the truss tubes, sleeves of heavy cloth over the truss tubes, etc...but I've never gone so far as to get that creative. Perhaps others who've done such will enlighten us.
Bill[/COLOR]

Floyd: the first thing I would look at is any flexure where your truss tubes connect to the mirror box or the upper. Stiffining this may kill the vibration, or may make it take LONGER to dampen but with shorter oscillations. Don't know the physics involved, but as you know I believe that a scope must first and foremost be stiff.

I am starting to work on my truss assembly for a 16" F5 Royce conical. As an experiment for now, I am going to attempt a 2.6" ma secondary for a lunar/plnetary optimized scope. 1/4 degree at 100% illumination will be sufficient. (I do have a 3.1 I can switch two and a second Protostar assembly should I opt for a less vigneted field).
To achieve this, I will need a diagonal to focal plane distance of aprox 11.5". But my concern is this:
My Feathertouch has 2" of travel, and (I am working with an UTA of aprox 17" ID). Will I be able to position my focuser close enough to the diagonal to reach focus without throwing the focuser tube into the lightpath, thereby defeating the point of an aprox17% CO. Clearly this is eyepiece dependent. I will be using mostly Radians and Panoptics. Any hard numbers on where these EPs reach focus relative to the focal plane of the primary?Or, will I need less focuser travel to avoid obstructing the aperture ... In other words cam I pull this off?
Joe

Floyd , give this a try:
If you can get your scope bottom heavy enough, place small 0.5 pound ankle weights (or equivalent) on the truss rods roughly near the middle. I used this set-up on a 15" dob. The results are amazing. The weights create "nodes" that dampen vibration dramatically. Furthermore they also double as sliding counter-weights to fine tune balance. A more refined version of this approach is one of the design modifications (hacks? ...LOL)that I will be incorporating into the truss structure for my 16" Royce conical (which he just finished!). Like you, I am trying to go with some novel approaches, such as an eyepiece accessible collimation mechanism.
Joe