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Pebble Hill Observatory

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#1 JoeT6571

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Posted 28 June 2012 - 05:51 AM

After 25 years of lugging and transporting my gear for observing, I finally live in a location that allows me to build an observatory. I've decided to build a 12' x 16' roll off roof observatory with a 5' x 12' add-on garden shed to keep my wonderful wife happy.

I struggled with deciding whether to go with a poured concrete slab or put the observatory up on sonotube footings. I decided to go with an elevated observatory on sonotube footings because of the drainage pattern on the property. Lots more on this later.

The site is pretty dark. We live on 40 acres three miles from a small town in far northern Wisconsin. There is slight skyglow to the east from town but it is not bad. Half of our property is field, the other half woods.

Of course the first thing one must do after laying out the location is to dig a hole for the pier. Out comes the shovel and four inches down I hit a my first pebble.



Not to be denied, I continued to dig to find the size of the beast. It was a little larger than I anticipated.

To be continued.

Joe

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#2 csa/montana

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Posted 28 June 2012 - 07:54 AM

Congratulations on the start of your Pebble Hill Observatory! Wow! If that's a pebble, I'd hate to see what is considered a boulder! :lol:

#3 Greyhaven

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Posted 28 June 2012 - 10:02 AM

Wow! With the size of the crater maybe that's a "meteor-wrong" right. :lol:
Hope you don't find more.
Be Well
Grey

#4 rwiederrich

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Posted 28 June 2012 - 01:57 PM

Congrat on your new Observatory.... :bow:
Also, congrats on finding bolder..just think of all the trouble it might have caused if you hadn't discoverd it right under your new Observatory :roflmao:

Rob(good to know your new OB is built on solid rock)

#5 Starman27

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Posted 28 June 2012 - 02:54 PM

So there you were..wondering where to dig the pier footing and... Good luck on the rest of your build and keep us posted.

#6 JoeT6571

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Posted 29 June 2012 - 07:02 AM

Thanks for the encouragement folks. Todays post is entitled adventures with Quikrete.

That pebble wasn't going to stop me because I knew I could call on my friend John to lift it out of the way. So off I trudge to the pole barn and fire up the John Deere. I lift the pebble out with a chain attached to the bucket in front and continue digging, and digging, and digging. My plan is to bury a 2' x 2' x 1' form five feet down. I wanted the top of the telescope pier base to be well below the frost line. It gets cold here in Hayward, Wisconsin.

About 3.5 feet down I hit hardpan. It is so hard I have to virtually chisel my way down. Definitely not fun. Finally I hit bottom, set my form and drive three steel bars of 6 foot long re rod into the middle of the form which will tie the base to the pier and reinforce the pier. My wife and I mix up and pour six 60 pound bags of Qwikrete into the form and let it all set up for a couple days.

Everything looks good, so now I put a seven foot long, 12 inch diameter sono tube on the base and backfill the hole. The top of the tube is three feet above the ground. This pour also goes well and I top the pier by driving a circular form with 3/4 inch treaded rod into the top. This circular form will be used to fabricate the base of the steel pier.

As my lovely wife drives out to go to town, I notice something strange about the pier. The tube feels very damp and could it be, is this thing starting to list to port? Sheer panic sets in, this baby is going to tip over and spill its guts all over the ground. Is this why they have a cute little picture of a support form printed right on the side of the sono tube? Why, oh why, was I so stupid to think that a cheap little tube of cardboard would support several hundred pounds of dripping wet concrete by itself?

By now panic has revved up to sheer terror. I race a couple hundred feet to the pole barn, grab some scrap lumber, nails, hammer, and sledge hammer and race back to my beloved project. Have you ever tried to build a square frame to fit a round tube while using your butt to hold up a listing sonotube? At any rate I manage to get it all built, supported, and even get that tube shoved back to vertical.

Note in pictures who is doing the heavy lifting.

To be continued.

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#7 csa/montana

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Posted 29 June 2012 - 08:55 AM

I race a couple hundred feet to the pole barn, grab some scrap lumber, nails, hammer, and sledge hammer and race back to my beloved project. Have you ever tried to build a square frame to fit a round tube while using your butt to hold up a listing sonotube?



Now, THAT'S the photo we would have loved to see! :roflmao:

BTW, we have neglected to welcome you to Cloudy Nights! Really enjoying your thread!

#8 Starman27

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Posted 29 June 2012 - 12:06 PM

This is just the start of the adventure! We have all been through similar opportunities to improve our skills and knowledge. :lol:

#9 rwiederrich

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Posted 29 June 2012 - 01:01 PM

Sweeeeeww. :foreheadslap:

Now is a good time to assess the small things needed to finish this project...before another problem occures that requires demolition.

Measure twice..cut once.

Glad you got things fixed.

Good luck.

Rob

#10 JoeT6571

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Posted 30 June 2012 - 11:42 AM

It was time to call in the reinforcements. My good friend Troy who lives way up in Hovland, MN (20 miles from Canada) has built two different cabins on concrete piers. He was willing to come down for the weekend to jump start this project. The plan was to lay out the sonotubes on Friday, dig holes on Saturday, place and backfill the sonotubes on Sunday, and pour concrete on Monday.

Troy came up with a very unique way to lay out the project. The idea is to construct a wooden frame from 2 x 4 material to the exact outside dimensions of my sonotubes. We use this frame to spray paint hole locations, pull the frame away, dig the holes, and then replace the frame over the holes. We then cribbed the frame to the desired height, establish proper levels with a transit, square up everything, and then tack the sonotubes to the frame. The frame allows us to support the tubes and keep them vertical during the backfilling and concrete pouring operation.

I wanted to elevate my observatory to keep critters from living underneath, keep air circulating below to keep the wooden foundation from deteriorating, and allow natural drainage.

What is better than a friendly neighbor? Answer: A friendly neighbor who owns a skid steer and is willing to help. I reserved a post hole digger attachment from the local rental center and we hooked it up Saturday morning. After my telescope pier digging experience, there was no way I was going to try to dig all those holes by hand. Who knows how many more pebbles we were going to encounter.

The frame construction went very well. The digging went very well. It was what happened later that did not go so well.

To be continued.

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#11 JoeT6571

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Posted 01 July 2012 - 05:55 AM

The digging was not entirely without adventure. We did run into a few more pebbles. Here is a collection after we lifted them out with a chain and dragged them off to the side.

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#12 JoeT6571

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Posted 02 July 2012 - 06:32 AM

After the holes were dug, we dragged our frame back over the holes and cribbed it up to the proper elevation. We used a transit to make sure the frame was level. The tops of the sonotubes will be attached to the top of the frame on Sunday. We also made sure everything was square. As I mentioned before the frame was designed to have two sides of each sonotube supported at the correct height and exactly where my 4 x 5 support posts will be centered.

One nice thing about the sonotube frame was everything was screwed together. When dismantled all lumber will be reused in the construction of the observatory. Little to no waste.

So far so good. It was time to BBQ steaks and drink beer.

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#13 JoeT6571

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Posted 03 July 2012 - 02:57 PM

Full disclosure - This post describes events that happened over a month ago. I did not want to begin posting this thread until I actually felt there was a chance I would be successful in this project. As you will see, there were some real challenges and at one point I really felt the project wasn't going to happen.

The next day (May 20, 2012) we woke up to clouds and the threat of rain. Since I only had Troy for the weekend, we decided to proceed with attaching the sonotubes to the frame, getting them vertical, putting some gravel at the bottom of the tubes, and backfilling the tubes.

We immediately discovered that some of the holes needed to be expanded. Occasionally while we were digging with the skid steer, the auger would hit a large enough rock to shift the auger over. To keep our holes in the proper place, we had to hand dig out the rock and expand the holes so the tubes would be vertical and in the proper position. It was quite a job.

While doing this work, it started to mist. We kept working. Then it started to gently rain. We kept going at a little faster pace. Then it started to POUR, and the site turned into a mess. We finished as best we could setting the tubes and pouring 4 inches of gravel in the bottom and around the base of each tube.

That night it rained 3 inches. The next morning to tubes were flimsy and soaked. The site (because of heavy soil) was a disaster. There was no way I could pour cement. Troy left Monday morning (May 21) and all I could do was wait for things to dry out.

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#14 JoeT6571

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Posted 04 July 2012 - 02:08 PM

After two sunny days, things begin to dry out. I haul a trailer load of sand from the local sand and gravel pit and use it to mix with my soil to backfill the rest of the tubes. Amazingly the sonotubes survive the heavy rains and I feel confident they will hold up ok. We mix and fill all 16 tubes in about 4 hours.

The picture shows the tube layout for the observatory, attached garden shed, and the gantry. I went with 8 inch tubes only after my local architect assured me they would carry the load. They are buried almost 4 feet deep and sit on about 4 inches of gravel. They stick out of the ground from 8" to 16" due to the slope of the ground.

#15 JoeT6571

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Posted 04 July 2012 - 02:11 PM

Missed the picture in the previous post

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#16 JoeT6571

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Posted 06 July 2012 - 06:40 AM

Disaster strikes. It had been a very wet spring and our ground was saturated. My wife's rain garden was full of water and local rivers were way up. One of the reasons I chose putting the observatory on piers instead of a floating slab was I did not want to build my site up enough to get good drainage away from the building. I felt I could just let the water run under the building by elevating it.

We got over 6 inches of rain in a month. I live in an area that normally gets 30 inches of precipitation in a year. After pouring my tubes the rains returned. It rained and rained and rained. My site was so wet that even with tubes buried 4 feet down, they were unstable. I had a pole barn full of lumber and started thinking about using it to build an ark instead of an observatory.

This was the low point of my build. I had serious doubts about success.

I knew I had to keep water away from the site. I dug two trenches to divert water away from the building site, lined them with landscape fabric, and filled them with sewer rock. I also covered by building site with thick plastic sheeting and covered it also with the same rock.

Luckily my skid steer neighbor also owns a small dump truck. He let me use it to haul the rock and I spread it with the tractor. This work was done in one long day.

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#17 JoeT6571

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Posted 08 July 2012 - 07:28 PM

Finally in the last week of June, I was able to start construction of the wooden foundation. The rains have let off and the site is dry. I have a vapor barrier installed and the diversion ditches and base are covered with rock.

The foundation is 2 x 8 treated timbers mounted on 4 x 6 (actually 3.5 x 5.5) posts. Even with trying to level the tops of the sonotubes, I still had a slight differential in the tops of the tubes. I leveled everything by mounting everything to the posts. I have a double beam running down the center. Joists are 16 inches on center all attached with joist hangers.

This part is easy and fun.

#18 JoeT6571

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Posted 08 July 2012 - 07:29 PM

Here is a picture of the wooden foundation.

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#19 csa/montana

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Posted 08 July 2012 - 11:17 PM

Glad the rain stopped, and you're able to continue the build! It's looking great; we appreciate the pictures!

#20 dw310

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Posted 08 July 2012 - 11:22 PM

Yep. This is fun to watch! Keep it coming!!

#21 JoeT6571

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Posted 09 July 2012 - 06:16 AM

Before setting the joists, I used concrete anchor bolts to attach the wooden posts to the concrete tubes. The wooden posts allow me to get the exterior and interior beams vertically level. The concrete anchor bolts allow me to square up the structure completely before permanently anchoring it down. The metal corners are cut to fit with a sawzall with a metal cutting blade. After squaring up my perimeter, I drilled holes into the concrete with a hammer drill, blow the dust out of the hole, hammer the anchor bolt down, and then tighten the nut on the anchor bolt. Tightening the nut expands the bolt in the concrete and anchors it completely.

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#22 JoeT6571

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Posted 09 July 2012 - 07:35 PM

I applied one coat of primer and a coat of paint to the underside of my 3/4 inch OSB tongue and groove decking prior to installation. Even though the deck is elevated off the ground, and there is a layer of plastic underneath, I felt the paint would help preserve the wood. The decking was glued and screwed on June 24. I made sure no 4 corners met by starting the second run with a half sheet.

I cut a hole in the decking for the pier leaving and extra inch. The pier is completely independent from the observatory.

Last summer we had a couple fairly strong windstorms. Each storm blew a couple of our mature aspen into our field. I had to clean them up because a local farmer cuts hay in our field every summer. Instead of continuing to "waste" this wood, I decided to cut 35 cords of aspen last winter from the perimeter of our field. Hayward has a large OSB plant and I had the wood delivered there. Since the decking (and the siding) I purchased from the lumber yard was made by this same company, I'm telling everyone some of the wood for the observatory came right from our property. That's my story and I'm stickin' to it.

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#23 Raginar

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Posted 10 July 2012 - 08:54 AM

Beautiful!

#24 JoeT6571

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Posted 10 July 2012 - 01:07 PM

The north and east walls were pretty straightforward. I went with 2 x 4 construction because of cost. Everyone assured me that 2 x 6 lumber was totally unnecessary for the walls. Studs are 16 inches on center. I framed up the wall on the floor of the observatory, squared up the wall taking diagonal measurements, and attached a temporary diagonal 2 x 4 to the wall to keep it square.

My plan is to complete the observatory before beginning the attached garden shed. Sorry dear.

I'm looking a rather happy here because things are finally starting to go well.

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#25 nytecam

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Posted 10 July 2012 - 03:46 PM

It will be fabulous - keep up the good work :grin:






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