I started construction by laying out where the observatory would be located. Then used some spray paint to outline the hole I would need to dig (3x3x3 foot). There is a lot to consider when planning this out. My observatory will be a remote use only. It will not be used visually and I will not be operated from within allowing for a pretty small footprint.
The hole was pretty difficult to dig. The soil is mostly clay which is like rock when dry and sticks to the shovel when wet. After 4 hours of digging I was only about 12" deep! I also had to contend with some old post hole concrete plugs (seen behind the hole). Over the next 2 weeks I alternated between shovel, pick, and post hole digger to excavate the hole.
Three feet seems a lot deeper when you dig a big hole! I would swear I was done only to find I needed six more inches. Here is an image of the finished hole.
I used some guide strings strung across the hole to get the rebar structure as close to center as I could. I used 3/8" rebar to construct a cage to add some strength to the stucture.
Since my observatory will not be used visually, the pier did not need to be very tall. The rebar only came above ground level by two feet.
When searching the web for ideas I found a guy who had an instant mix concrete company come pour his concrete pier. I searched for one and found one locally (search for Mobile Concrete). This was a saving grace. After spending 2 weeks digging I really wasn't up for mixing 45+ 80 lbs bags of concrete (not to mention the trips to go get the bags). The cost was $220 for a yard of 4000 psi concrete and it was worth every penny.
I used a drywall knockdown knife to smooth out and level the concrete.
I purchased a pier plate from Dan's Pier Plates. I mounted it to a piece of scrap 3/4" plywood so it would sit on top of the Quik-Tube securely.
I bagged the pier plate to keep it clean and concrete free.
I created a quick 2x4 structure to hold the Quik-Tube in place as the concrete is added.
Once the block was poured I waited an hour and a half to setup for the concrete pier. I checked at an hour but it was no where near ready (your time may vary). I actually wish I had waited longer. The block bulged a bit around the Quik-Tube when I started. I stopped after one bag and smoothed out the bulge. Twenty minutes later I finshed with the last two bags.
I hand mixed the three bags for the tube part of the concrete pier. Make sure to read the instructions for doing this. The concrete mix needs a very specific amount of water to get it right. Too much or too little can make the concrete weak or worse, crack and crumble. Be sure to tamp the concrete down and rap on the sides to get the air bubbles out. I spent quite a bit of time doing this and still ended up with a few small voids.
Note the red paint mark near the wheelbarrow. That was my "North" indicator. The night before I placed a string from the rebar to the direction of Polaris. I replaced the string with some spray paint prior to pouring the concrete so I didn't accidentaly disturb it.
You can't see in this picture, but I left about 3" of space between the top of the concrete and top of the Quik-Tube. I slowly pushed the pier plate down into the concrete with a twisting motion until it contacted the top of the tube. I double checked the plates alignment with my red "North" indicator and that was it.
I left the Quik-Tube on for three days before I removed it. I probably should have left it on longer as the sides were still a bit damp. It cured the rest of the way without cracking and it is solid and ready for use. It was a lot of work to get to this point but I have been wanting to do this for 15 years. Next up, observatory construction.
I built my observatory based on Sky Shed plans. I altered the plans in a few steps to meet my needs but kept to the plans quite a bit. The foundation for my observatory is free floating (not directly anchored). This will help to isolate it from the concrete pier to reduce vibrations. I used four 4"x4"s leveled and placed on 1'x1' patio stones.
I used 1"x10"s to construct the floor. I took great care to make sure the floor was square (checking it after each board). I used 3.5" deck screws to secure the boards to the foundation.
Note: I used screws for the entire construction. I do not own a nail gun so power driving the screws with a drill was the next best solution. This also increases the strength of the structure somewhat.
This is the observatory floor nearly completed. As I got the end, I only needed a 3"x1" board and didn't want to rip a 1"x10" to make it. I finished up the floor a bit later after another run to Home Depot.
I then started construction of the walls. I used two 4"x4"s in place of 2"x4"s in a few places to help support the roll off roof.
I used lag screws to secure the 4"x4"s. I also pre-drilled some pilot holes to aid in getting the screws set squarely.
Here is the end wall. It has spaces on each side that will allow the roof to roll by.
Pre-assembling the walls made hanging them pretty easy. I did all of the construction solo, so I used some straps here and there to secure items together while I placed the screws.
Here is a shot of the three walls installed. I was still deciding what to do about a door so I waited to construct that wall until later.
I was pretty happy with how the walls came together. The alignment and height was perfect.
The next step was to build the supports for the roll off roof. I had to invade my wife's garden a bit but I didn't cause too much damage.
During one trip to Home Depot, I ran across these supports and thought they would be perfect for helping to level the support 4"x4" (during construction and later when it settles).
I put all of the support structures in place and used a temporary cross support to get everything square and level. I then poured a 80 pound bag Quikrete in each hole and added water (fence post instructions).
I then placed the tracks that will hold the roll off roof. These are just regular garage door tracks. I purchased mine online at Grainger. You can also kind of see the final wall in place (in the foreground).
This is a shot of the support structure. I used 5" lag screws to connect everything.
The roll off roof was assembled and installed in a day. I used a 2"x6" for the ridge.
Here is a closer shot of the roof showing the angle cuts. I'm glad I have a compound miter saw. That made the 22.5 deg cuts much easier.
Here is a close up of the rollers that support the roof.
Here's a shot of the observatory with pressure treated 1/2" plywood mounted.
Now time to finish the roof. I used 1.5" aluminum drip edge and an overlapping leak barrier.
Here is a shot of the roof with shingles installed.
I started the finishing work by installing the trim. I used 1"x4"s for the trim and door jam.
After finishing the trim I started on the siding. I used 12" siding found at Home Depot. They came in 16' lenghts, so I had them cut in half to make them more managable.
Here is a shot with the back side finished.
I completed the lower part of the observatory in about a day. I ran short of siding for the roof section so decided to call it a day.
I finished up with the roof section and added some extra trim to act as a weather barrier.
After all the work to get here, painting was a snap. I still need a door and some weather stripping to further protect the interior but I can see the finishing line.
Here's a shot of the door. It is built per the plans except I added a 1/2" plywood sheet to the back for more strength. I also added some extra security devices, lights and a third spring loaded hinge after the picture was taken.