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Suggestion on the design of a roll-off roof observatory foundation (slab)

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#1 syxbach

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Posted 19 January 2021 - 10:02 AM

Hello folks

 

I am so excited that I have connected to Scott from BYO and his team will come to West Texas this spring to build an observatory in our club's ranch. We decide to go for a concrete slab foundation because we think this is much stabler. I have asked a local builder to make a concrete pier in my backyard, which did not require a detailed design. How I need 4 10-inch piers plus a 15.6 ft by 15.6 ft concrete slab. I also need the 4 piers to be separated with the slab. Any suggestions? I would very appreciate if you can provide any suggestions (such as footing, frost line). I am not familiar with construction and made an ugly drawing which looks not professionallol.gif

 

Best

 

Yuexiao 

 

 

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Edited by syxbach, 19 January 2021 - 10:04 AM.


#2 fbzolt

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Posted 19 January 2021 - 11:28 AM

Hi,

 

  My observatory built by BYO was large enough to require plans and a building permit with inspections.  I worked with a local general contractor that has done a lot of previous work for us (and put down the slab and electrical/finish work in the warm room) to get the drawing done to local specifications and had them sealed by an certified SE to make approval easier.  I don't know what your local building code requires, but in my case the building was over 120 square feet, so plans/permits were required.   The drawing had cross section and rebar specifications.  The pier locations/hole in the slab were noted, but were not of a concern to the county for permits.  BYO dug out the holes and installed the piers in the provided openings.  If you PM me, I can send you a copy of my slab plan I had to submit.  You local codes may require more or less.

 

Thanks,

Frank Z... 



#3 macdonjh

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Posted 19 January 2021 - 03:16 PM

Cool project.

 

I suggest looking for the thread "Pier Engineering" in the Observatories forum.  It will provide lots of good information about piers.  Spoiler: I wouldn't do what you show in your sketch.  More work than necessary.  As for frost line, while I doubt you'll have to worry about it in West Texas, talk to the local building inspectors and find out what it is for real.

 

Isolating the piers from the floor is as simple as leaving a hole, slightly larger than your pier, in the floor when it's poured.  Your concrete contractor will be able to do that for you.  I filled the hole around my pier with 1"-2" loose rock.

 

Before you finalize your design, I recommend setting up the four mounts and scopes your club plans to install (or close equivalents) at the spacing you show in your sketch.  Set up boxes, chairs, tables to simulate the walls of the observatory.  Then get as many people as you imagine will use the observatory simultaneously and have a dry-run star party.  You may find your plan is perfect.  You may find you want to modify the space between the piers, the building size, whatever. 

 

To expand on fbzolt's comments, it is worthwhile in my opinion to plan for underground conduit and wiring between the wall(s) and the pier(s).  I ran three conduits: one for 120V AC power, one for 12VDC power and a third for USB/ ethernet signals.  No cords running across my floor.  It is wonderful.  And easy to do as long as you do it before the concrete is poured.

 

Good luck with your project.


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#4 speedster

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Posted 19 January 2021 - 11:59 PM

Where in West Texas?  I'm in Abilene and no organization over here. 

 

if you are inside a City's jurisdiction, you'll have to have drawings and meet code.  If not, you can do whatever you want.  Slab depends on soil type.  The pier engineering thread will tell you a lot.  Ditto on the conduits.  I suggest two 1" or larger to each pier.  Also ditto on the mockup.  You might find 4 operators and 4 telescopes a bit tight.  After you go through the pier engineering thread, if you have questions, feel free to PM me.


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#5 syxbach

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Posted 20 January 2021 - 08:43 AM

I am from Lubbock. The dark site is in Guthrie, TX, in the middle of nowhere. I asked my club president, and he said no code requirement in our ranch. Will look into pier engineering thread for details.

 

Thank you!

 

Best

 

Yuexiao

 

 

Where in West Texas?  I'm in Abilene and no organization over here. 

 

if you are inside a City's jurisdiction, you'll have to have drawings and meet code.  If not, you can do whatever you want.  Slab depends on soil type.  The pier engineering thread will tell you a lot.  Ditto on the conduits.  I suggest two 1" or larger to each pier.  Also ditto on the mockup.  You might find 4 operators and 4 telescopes a bit tight.  After you go through the pier engineering thread, if you have questions, feel free to PM me.



#6 macdonjh

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Posted 20 January 2021 - 02:37 PM

Pretty good skies in Guthrie?  Do you have to chase off people from Dallas (I'd let Ft Worth observes in, but not those from Dallas...)?



#7 t-ara-fan

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Posted 20 January 2021 - 03:32 PM

  • Is there going to be control room? What we call a warm room but you might call a cool room wink.gif
  • Lots of conduit under the floor to the scopes.
  • Are these scopes for visual or OP? If the latter, where are the desks and computers going to go?
  • The spacing you drew means 2.6' clearance between piers, and 5.2' from piers to the wall. You could even out those numbers with a 7.8' distance between piers.  Or are you loading the walls with equipment, shelves, etc. 
  • I am a fan of pouring concrete into an open hole, rather than pouring into a form and then backfilling the soil.

Edited by t-ara-fan, 20 January 2021 - 03:33 PM.


#8 syxbach

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Posted 20 January 2021 - 04:14 PM

No control or warm room. We have a house there which provides electricity, heat and water.

 

These are strictly for astrophotography. No visual at alllol.gif

 

There are only scopes, mounts, cameras, computers and other necessary electronic devices in that room

 

What I plan is to dig 4 big holes, pour concrete, and make piers first, then add dirt and make the slab.

 

 

 

 

  • Is there going to be control room? What we call a warm room but you might call a cool room wink.gif
  • Lots of conduit under the floor to the scopes.
  • Are these scopes for visual or OP? If the latter, where are the desks and computers going to go?
  • The spacing you drew means 2.6' clearance between piers, and 5.2' from piers to the wall. You could even out those numbers with a 7.8' distance between piers.  Or are you loading the walls with equipment, shelves, etc. 
  • I am a fan of pouring concrete into an open hole, rather than pouring into a form and then backfilling the soil.

 



#9 syxbach

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Posted 20 January 2021 - 04:17 PM

Really dark. If you go outside during the night, you see nothing. My club members say the place can approach class 1. I do not understand why I have to chase off people from Dallaslol.gif  It is just ~3.5-hour drive. One pier user will be from Dallas, one will be from Austin.

 

You can see some of my posts showing some images taken from that ranch

 

Yuexiao 

 

Pretty good skies in Guthrie?  Do you have to chase off people from Dallas (I'd let Ft Worth observes in, but not those from Dallas...)?



#10 speedster

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Posted 20 January 2021 - 11:20 PM

Excellent choice of Guthrie.  For those not fortunate enough to live in the Lone Star State, Guthrie is the headquarters of the Four 6's ranch.  It's not even an incorporated community.  Only 126 people live there.  In all of King county, about 1,000 square miles, only 286 people on the census and not a single incorporated community.  The ranch itself is 1/3 the size of Rhode Island but, this being Texas, it barely makes the top 10 in terms of size.



#11 sberrada

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Posted 24 January 2021 - 11:58 AM

I agree with Tara fan about spacing - i would suggest to go with 6’ or so between piers.
Mine is 5’ and it can get into interference with 2 scopes that are 40-48” long because:
- scopes are not centered on saddle
- nature of equatorial mounts is such that RA motion can bring scopes closer together.

It boils down to size of scopes you want. I have a TOA130 and edge 8 (with dew shield) and found that they get very close at times and could interfere

Good luck
Sam

#12 DeanS

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Posted 24 January 2021 - 12:11 PM

Here is a more flexible idea.  Pour 4 individual deeper pads in each area you will have a telescope.   Maybe 2'x2' or even larger will give some flexibility for spacing as needed.  These should be same level as the rest of the pad only isolated with foam or whatever.   This way each person can have a metal bolt down pier of their choice.  Once you make concrete piers it is not easy to change.  

 

Advantage is you could pour everything at once, and if way down the road the building becomes something other than an observatory it has a flat floor.

 

Dean


Edited by DeanS, 24 January 2021 - 12:13 PM.



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