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 Telescope mounting pier, tall concrete pier
 
leftcoastgene
post Jun 11 2008, 11:24 AM
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I recently purchased a surplus observatory dome (Ash) and I'm designing the observatory. The current thinking is to build a two story structure about 12 feet in diameter. As the telescope will be mounted about 12 feet off the ground, I'm thinking of a large concrete footing with a central pier (maybe concrete filled culvert pipe) with a base plate at the top. I want to minimize any vibration / movement from the structure to the pier, as the structure will probably be metal stud / corrugated metal siding (flexible). Any advice? Glad to have found this amazing site. I know I live in the city and the lighting is miserable, but that's what I've got right now. Many thanks.

Gene Chapo
Encinitas, California
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Ron Walker
post Jun 11 2008, 11:54 AM
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I'm not an expert, but common sense would tell me that the taller the pier the larger it should be in diameter and also the further down into the ground the substantial concrete base should go.

Also it would depend on the size of the scope you plan to put on the pier. I remember reading something about the pier diameter being equal to the scope aperture but I believe that only held true for shorter piers. Twelve feet is a tall pier.

Obviously you observing floor should not make contact with the pier at all.

I'm sure others with more experience in this will join in soon.


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Ron Walker

Orion 11" XLT EQ-G ~ Orion 102mm Mak
Burgess 38mm ~ Stratus 21mm and 13mm
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Greg Mueller
post Jun 11 2008, 11:55 AM
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Wow! a surplus Ash Dome? blink.gif

It sounds like your's and mine will be almost the same.
If I were to do mine again i would do a couple things differently.

Excavate down below the frost line and make a flat compacted surfaced (undesturbed soil would be best) Make the excavation big enough to work with clearance all around.
Make square forums and pour a huge block of solid concrete, about 6' square and 3' deep. Put rebar in it and sticking out the top to tie down your column. Make sure the top of the big base is 6-8" below ground level. Build a column of cement blocks about 4' sqaure on top of the big block. Go up as high as you want. Grout the blocks solid. Leave the center hollow. Use rebar in the blocks. Use plywood down from the top of the blocks about 6" and fill the top with cement and rebar tieing it to the walls of the column. Get some Stainless steel "L" bolts in a large size (5/8" or 3/4") and arrange them in a bolt pattern using a sheet of plywood with the "L" bolts bolted through it. When the cement is hard take off the plywood and replace it with a "weld to" plate (I plan to use 1" thick steel plate).

Get some sheet foam or spray foam and cover "the big block" with it thoroughly. Wrap the column with foam (I use blue 6" wide foam from Home Depot that goes under the bottom plates of house/garage walls). Wrap the foam around and round the column so it's about an inch thick. If you do it right you will be able to skreed using the top of the blue foam and the edge of the foundation wall forms

Next pour your foundation slab/walls/footings that the walls will sit on. Round or not.

All the foam will isolate the column/big block/scope from the walls/floor/dome.

Put some 2" gray (pvc) conduits in the forms so you can bring in power and communication wires

When the concrete is hard, grab the end of the blue foam that is wrapped around the column and pull it out. It will leave a gap between the column and the floor.

Build walls
Sheet with corrugated steel
Mount dome

Happy days


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Soon to be living in The Land of Enchantment
Range 12W Township 3S Section 8
Watch construction at http://www.section8observatory.com/
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SteveDurham
post Jun 11 2008, 08:53 PM
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I don't have a clue.....However....
I would agree with the big solid concrete base, but I'm not so sure about the 4 foot square of cement block. IMHO, that would create a HUGH heat sink that once warmed would take forever to cool. Thus allowing heat vapors to swirl up around the scope.

I think I'd go ahead and build the big cement pier foundation and yes, keep it underground, From there up, I would try to use two pieces of galvanized culvert pipe, one inside the other and held centered to it. This column, I would pour solid concrete to make a tube of concrete, say 18 to 24 inches OD with a wall thickness of 2 to 3 inches. I'd then top this off with a steel plate that would accept a secondary metal pier, say one of the adjustable height ones.

This is just an opinion, and it's my guess we all have one.

Just be sure to take plenty of pictures and post em here so we can OOOO and AAAAh along with the construction!!!

Steve
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Greg Mueller
post Jun 12 2008, 08:09 AM
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I took some clues from the observatories in NM at Apache Point. My first Idea was to do the thing with culverts, but they got real expensive and the sizes available wouldn't let me have the wall thickness I wanted. I looked into sonotube but they didn't have any the right diameter and length. Here's a pic from Apache point. Notice the huge column and the open air walls. I figure solid metal walls would keep out the sun and help keep the column cool. I have seen people insulate the column with furnace duct insulation. My column wound up at 40" square.
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Attached File  observatory.jpg ( 41.42k ) Number of downloads: 5
 


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Soon to be living in The Land of Enchantment
Range 12W Township 3S Section 8
Watch construction at http://www.section8observatory.com/
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leftcoastgene
post Jun 12 2008, 05:18 PM
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Wow, you guys have been so helpful. I think the way to go is certainly the concrete block core isolated from the skin of the building and the observatory floor. I have always had an interest in Astronomy and hoped one day to build an observatory. The domes (there were two) came available on Public Surplus website that handles schools predominantly. I knew this was my chance. The school was a local JC, Palomar Community College, that has a pretty good Astronomy curriculum. It seems they are demolishing most of their '60s vintage buildings and the planitarium and the 2 observatories. I spoke with the guy who bought and took down the first one last Sunday. He was very helpful in sharing clues to take it apart without destroying it. I have spent 2-3 hours for the last few days taking the dome apart. This afternoon it is safely on my property, all parts acounted for.

I will speak with the other purchaser soon, and I'll mention this site. He will be very happy to make contact with others interested in the skies.

I'll post pics occasionally. Right now I could only post a pic of a pile of sheet metal, motors and assorted parts.

Many thanks to all,

Gene Chapo
Encinitas, California
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Greg Mueller
post Jun 12 2008, 05:37 PM
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What a loss for the community, but a score for you.
Did they say if they planned to replace them? What kind of equipment was in them?
Is it motorized? What diameter?


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Soon to be living in The Land of Enchantment
Range 12W Township 3S Section 8
Watch construction at http://www.section8observatory.com/
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Ron Walker
post Jun 12 2008, 05:53 PM
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We love pictures of piles of parts! huh.gif


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Ron Walker

Orion 11" XLT EQ-G ~ Orion 102mm Mak
Burgess 38mm ~ Stratus 21mm and 13mm
Dyanscope 4" (1950's vintage)
Nikon F 35mm ~ Canon 300D

Planetaria:
Goto E-5 (Viewlex) ~ Spitz A3P ~ Minolta/Viewlex Series II B
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NeoDinian
post Jun 12 2008, 06:24 PM
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QUOTE(Greg Mueller @ Jun 11 2008, 12:55 PM) *
Wow! a surplus Ash Dome? blink.gif



They exist...

My local club bought a dome from Ash in 1980... The dome was ORIGINALLY supposed to go to Iran (some rich arab). Of course that was also the time of the Iranian hostage crisis... So Ash did NOT ship the dome (and the Government wouldn't let them anyways if they wanted to!)... The Dome was half paid for already, so the club was only charged the remaining half! smile.gif



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Greg Mueller
post Jun 14 2008, 09:59 AM
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PS

Don't think for an instant that any contractors that you use will have a clue as to what you are doing. Be there to supervise every minute, even if it seems obvious to you and you draw them a picture and have photographs. Most of the time they consider plans and what not merely "guidelines". angry.gif


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Soon to be living in The Land of Enchantment
Range 12W Township 3S Section 8
Watch construction at http://www.section8observatory.com/
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leftcoastgene
post Jun 14 2008, 01:07 PM
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Thanks, I've seen it a lot myself. I am an architect here in California and I see a lot of misinterpretation of drawings. No one likes to do construction twice, but it happens. I can lay block (not fast), so I plan to do that part. I hope I can follow my own plans.
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