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Maybe a slightly different wooden pier approach

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#1 astrobeast

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Posted 13 August 2021 - 11:51 AM

I recently completed installation of a pier for my Celestron CGE/Edge 11 scope. My approach is a sort of hybrid developed from reading a number posts here and so thought I'd show people what I did.

 

Typically, I see when people are forming wooden piers, they are bolting them to the top of a concrete base. In my case, I decided to embed the pier itself into the ground to simply the process. Obviously I have lost the option to move the unit (or at least easily) but for my life situation, this is not a concern.

 

The pier is made from 4 sections of 2”x8” lumber that have been glued and screwed together at the edges to form a box, so the outer dimensions are ~9.5” square. One person I corresponded with suggested this as having the grains go in varying directions should make it stiffer and less prone to warping. The “tube” is about 64” long with the plan to put about 30” in the ground and 34” above (looking for approx 36” height to the top of  Dan's pier plate).

 

IMG_0831.jpg

 

I dug an 18” dia hole about 34” deep, put gravel in the base (although it's questionable whether this is really necessary), then added 400 lbs of Quikrete putting in a bag at a time with appropriate amount of water to insure good mixing. I have installed a lot of fence posts so was pretty familiar with this material and technique so this process went smoothly.

 

To help deaden any “ringing” of the pier, I filled it with general purpose sand from Lowes. I have nothing quantitative to offer in terms the efficacy of this, but can say that there is noticeable difference in the sound from before and after when you rap in the side of the pier, so all indications are that it will help to dampen vibrations.

 

IMG_1083.jpg

 

IMG_1165.jpg

 

The pier cap is a piece 3/4” oak that has been drilled to accept the top half of a Dan's Pier plate I found used on Astromart. As the mount head has built in Az and El adjustments, I didn't see the need to have the full system that permits the tilt compensation. I was careful to level the pier when pouring the concrete and it is very, very close to perfect.

 

IMG_1189 (1).jpg

 

I've order a Astrogizimos 365 cover and will get the mount and scope set up when it arrives.

 

So I have no feedback to offer at the moment as to how well this experiment will work, but can say that it is really rock solid as we like to say! I will be shocked if doesn't work very well, but will report back when I have the scope mounted.

 

 

 

 

 


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#2 matt_astro_tx

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Posted 13 August 2021 - 12:02 PM

Very nice looking pier.  Eager to hear how things progress.



#3 astrobeast

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Posted 13 August 2021 - 02:34 PM

Very nice looking pier.  Eager to hear how things progress.

Thanks! The 365 cover has shipped so hopefully in a few days I can have the mount and scope up and running and report on stability. 

 

R



#4 matt_astro_tx

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Posted 13 August 2021 - 03:34 PM

I'm now considering a pier for the GEM build I am in the middle of.  Latest post here.  I've considered doing the sonotube thing but I like the wood wrapped look much better.  Why did you choose to fill it with sand instead of just topping it off with concrete?

 

And, did you fill the bottom of the pier interior with concrete up to ground level and then fill the top with sand or what?



#5 astrobeast

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Posted 14 August 2021 - 07:44 AM

I'm now considering a pier for the GEM build I am in the middle of.  Latest post here.  I've considered doing the sonotube thing but I like the wood wrapped look much better.  Why did you choose to fill it with sand instead of just topping it off with concrete?

 

And, did you fill the bottom of the pier interior with concrete up to ground level and then fill the top with sand or what?

Sorry to take so long to respond, got sidetracked yesterday.

 

The center of the pier was not filled with concrete; it's all sand. The use of sand came from a recommendation from another poster a while back who made a similar structure (although he bolted it to a foundation rather than stick in the ground). 

 

As I mentioned in the OP, its purpose is to help deaden vibrations. Sand is an excellent acoustic attenuator and rapping on the side of the pier now as compared to before being filled gives a very different result. As I noted, this is all an experiment and so I have no quantitative analysis to say this was a better way to go, but qualitatively, the sand in the center appears to be a good approach.

 

Happy to answer any more questions, I'll looks to see if I have any further pics that illustrate what was done.

 

R



#6 kathyastro

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Posted 14 August 2021 - 08:17 AM

Nice looking pier.  As the owner/builder of a plywood pier, I have respect for well-engineered wood as comparable to other forms of construction.  I am sure you will get no appreciable vibration.

 

I am not a big fan of embedding wood in concrete.  The wood swells with the moisture in the concrete, then shrinks as it dries.  So there is almost always a gap between the wood and the concrete.  If the installation is exposed to weather, precipitation will get into the gap, no matter how small it is, and freeze in winter, expanding the gap.  The usual outcome after a few years is a split concrete block.

 

Still, it is a nice looking installation, and I hope it works well for you.  I'll be interested to hear how it performs.


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#7 astrobeast

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Posted 14 August 2021 - 08:34 AM

Nice looking pier.  As the owner/builder of a plywood pier, I have respect for well-engineered wood as comparable to other forms of construction.  I am sure you will get no appreciable vibration.

 

I am not a big fan of embedding wood in concrete.  The wood swells with the moisture in the concrete, then shrinks as it dries.  So there is almost always a gap between the wood and the concrete.  If the installation is exposed to weather, precipitation will get into the gap, no matter how small it is, and freeze in winter, expanding the gap.  The usual outcome after a few years is a split concrete block.

 

Still, it is a nice looking installation, and I hope it works well for you.  I'll be interested to hear how it performs.

Thanks! The look of a wood pier were part of decision to go this route, but not the main one, but now that it is done, I really like the appearance and should I ever make another pier, I would certain follow a similar path.

 

I've installed a number of fence posts using every conceivable approach and so far haven't had issues with splitting for those that are in concrete. I have been putting a bead of sealant around the joint between the concrete and the wood and it also helps to build up a conical top to the concrete so that the water flows off and doesn't pool. I will do something similar to the telescope pier, still deciding on what would look the best.


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#8 siriusarcher

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Posted 14 August 2021 - 11:52 PM

One thing I really like about this pier idea is that it will be easy to screw stuff to it, unlike a metal or concrete pier. The accessories you might want to mount on your wooden pier could include:

  • cable management hardware
  • power supply
  • mini-pc
  • eyepiece rack
  • hand controller cradle
  • cupholder 
  • bottle opener
  • master switch for power
  • bracket for a tablet


#9 The Ardent

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Posted 15 August 2021 - 12:08 AM

Is there a recommended sealant/protectant for the wood to apply once in a while?

#10 siriusarcher

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Posted 15 August 2021 - 02:41 PM

When you are exposing wood to moist conditions in soil, it is always a good idea to paint the end grain with something like copper chromium acetate (the same green-coloured penetrant used to pressure-treat the wood you used). Nothing else needs to be done to the wood although deck stain might improve the looks. If you are building an observatory over this pier, you'll be protecting it from most of the effects of weather so surface finishes will be mostly of cosmetic value only. 



#11 astrobeast

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Posted 18 August 2021 - 10:12 AM

 

One thing I really like about this pier idea is that it will be easy to screw stuff to it, unlike a metal or concrete pier. The accessories you might want to mount on your wooden pier could include:

  • cable management hardware
  • power supply
  • mini-pc
  • eyepiece rack
  • hand controller cradle
  • cupholder 
  • bottle opener
  • master switch for power
  • bracket for a tablet

 

Actually, this was one of the reasons I did go with a wooden pier. My 365 cover just arrived, but I off an on thought that I would eventually replace with the Scope Motel (from Dan's pier plates). And I noticed that a sizable fraction of the assembly was constructing a mechanism to grab the circular concrete pier. So this does make it much easier to add such an enclosure.

 

Also, I did soak the ends in copper chromium acetate.

 

 

R



#12 gpsfool

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Posted 24 September 2021 - 03:36 PM

That looks good - how's it working out for you? 

 

I built a wooden pier in summer 2020.  It's four 4x4's glued and screwed together in a square configuration - 7.5x7.5. This is concreted into the ground.  For the aboveground section I've coated it in spar varnish, the stuff used on boats - it was left over stuff I had in the garage. So far polar alignment has held up well and negligible vibration for my scopes. 

 

Hopefully it will be fully covered soon - currently having discussions with the town over a permit  - gotta love govt.

 

GPSFOOL



#13 tturtle

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Posted 05 October 2021 - 12:06 PM

This pier looks very nice and will probably hold up fine for many years in your climate. I wish we could do something simple like that down here in Fla but we get torrential rains that would probably make it rot away in a few years. 




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