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Buckets and sand as anti-vibration solution?

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#1 CrazyPanda

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Posted 07 October 2012 - 08:23 PM

I've been into astronomy for a long time, but currently do not have a telescope. I live in an apartment complex and while I have a nice dark sky, my only option is to set up a would-be future telescope on my wooden deck (there isn't any "yard" or area that isn't affected by the glare of security lights, my deck is shielded from that stuff).

After doing a lot of reading on the benefits and limitations of expensive VSPs from orion/meade/celestron, I was wondering if anyone in a similar situation has ever tried using cheap 5 gal. buckets filled ~half way with sand, and then putting some rubber/gel feet on the bottom of the pails to further reduce vibration transfer.

In theory a setup like that wouldn't cost more than about $10 (3 pack of 5 gallon buckets for a measly $7) and should be superior to those VSPs anyway. Sadly I'm in a bit of a catch 22, because without a telescope I can't test my theory, but I don't want to spend money on one right now if it's going to be more or less unusable due to being set up on a deck.

Thoughts?

#2 TxStars

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Posted 07 October 2012 - 10:45 PM

I think it is going to come down to how steady the deck is.
Could be wrong but I dont see how anything is going to help short of cutting a hole in the dec.

#3 Jon Isaacs

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Posted 08 October 2012 - 07:55 AM

Hello and Welcome to Cloudy Nights. :waytogo:

I can't help you with your quest... But if the skies are dark and there's a telescope, I would bet you could find a way to make it work...

Where do you live? Maybe some nearby Cloudy Nighter could help you try out your scheme.

Jon

#4 mich_al

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Posted 08 October 2012 - 08:21 AM

Welcome to CN. I observed from my elevated deck for about a year. I believe the issue is not so much vibration as it is the deck moving. Even the slightest movement will show up in the eyepiece especially as magnification goes up. My deck is attached to the house just above the foundation. I even wedged substantial timbers between the ground and the deck frame under my tripod. It helped but I could still tell when the cat walked up the steps on the other side of the deck. I don't think it is possible to stabilize a deck enough to not show in the eyepiece. All that said, most of the time the view is quite stable for visual and unless you or something else is moving on the deck or the wind is moving the house or deck its all good.

Al

#5 Quintessence

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Posted 08 October 2012 - 09:16 AM

Since your main problem is motion of the deck and not vibration within the telescope, the buckets of sand will not help. What you need instead is an inertial platform that is isolated from the deck. The idea is to let the deck move under the inertial platform while the platform itself "floats" in space.

Probably the best (inexpensive) thing to use as an isolator is some kind of dense rubber puck. I'm not sure exactly what to suggest -- but you are looking for a balance between compliance and stiffness. If too stiff, there is not isolation. If too compliant, the platform will rock uncontrollably. What you want is just enough compliance to allow the deck to shake relative to the platform. Rubber will work better than a spring because rubber will dissipate energy and not start bouncing as it absorbs energy from the deck. There will be trial and error tuning involved. Your will need to match the response frequency of the isolation system to the frequency of the deck. This can be accomplish by trying different isolators with different amounts of stiffness, and/or varying the locations and number of isolators. So -- expect the tuning process and don't give up if the initial result is not perfect.

So, the basic construction is simple and looks something like this:

Lay out your pattern of isolators -- then lay a thick piece of plywood over them. (The locations of the isolators are likely going to work best near the edges of the plywood sheet.) The plywood piece should be just large enough for you to erect your telescope on it. You do not want to stand on the platform. Then lay concrete garden "pavers" over the plywood to create a massive platform with lots of inertia. You can do some tuning by trying a single layer of pavers versus a double layer -- or even a third layer. But be mindful of creating too much load for your deck to handle safely. (Since the platform is not large, you should be able to safely build what you need.)

You will get the most solid support directly above one of the support beams on your deck. Also, if the support beams are cantilevered, then you will have more motion near the outer edge of the deck.

Some experimenting will be required -- and I'm not certain what to suggest for the rubber pucks. Some kind of pucks may exist for protecting delicate equipment while being transported in a truck. I'm not sure -- but this would be the kind of application that might have pucks with the correct properties.

Good luck,

Charles

#6 rmollise

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Posted 08 October 2012 - 03:36 PM

The deck will be a problem. Not sure what you plan to do with the bucket...if suspending it from the tripod is what you have in mind, that will help...but I'd use a water filled milkjug instead, and old idea that works.

#7 AlBoning

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Posted 08 October 2012 - 03:57 PM

I would give consideration to tripling the number of joists. It might solve the problem, it might reduce it to something conventional anti-vibration strategies can handle, or do nothing at all.

#8 roscoe

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Posted 08 October 2012 - 07:44 PM

Charles has a cool idea there! You might browse McMaster Carr (mcmaster.com, I think) for vibration supression stuff, they have a bunch of options.
Good luck with it!
Russ

#9 Pat at home

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Posted 09 October 2012 - 03:59 PM

The OP lives in an apartment. I don't think options that involve modifying the deck structure would be well received by the OP's landlord.

#10 frankart

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Posted 16 October 2012 - 10:48 PM

For visual not photo astronomy don't worry about vibration: hold your breath and don't move when looking at double stars. DSO's aren't as much of a problem at lower magnification. I set up on a wooden deck, took the pointy tips off the tripod and replaced them with plastic pipe caps, set up on rubber pads on concrete pavers, etc.. Best I can do. Sand pails don't help: been there, done that.

#11 JGass

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Posted 17 October 2012 - 04:16 PM

I observe from my townhouse's deck. One of my scopes on a Celestron SLT mount has a fair bit of vibration when I slew or adjust focus. The deck isn't the cause of that problem, but bear with me a moment.

I was at a dollar store recently, and noticed that they had Gel heel cushion and ball of foot cushion inserts for shoes.
These happened to be made of a clear gel. Since the cost was modest, I bought a couple of packs of the ball of the foot inserts to try under my tripod legs.

To my surprise, with these between tripod leg and deck floor, the vibrations damped out in roughly half the time than without the gel cushions. I plan on putting disks cut from these into rubber "floor protectors", the kind that go under table legs.

Will they also help reduce transmission of vibrations from the deck to the scope? Maybe somewhat. But, in my case, since they already help with the tripod vibration problem, I will use my < $5 anti-vibration pads regardless.

I may even experiment with doubling up these gel cushions to see if there is even more rapid dampening of the tripod shakes.






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