Observatory Construction

The observatory "warm room" and office are in a 14x30 metal building separate from the dome structure. It is also home to my electronics lab, and my other hobbies.
The interior of the building was originally bare 2x4's, so I had to insulate and finish it, which was done during 2022 - 2023.
​The observatory control and image processing computers are located in the warm room, and connect through a gigabit network with another computer in the dome. The dome's Ethernet connection is from an underground cable connecting with an Ethernet switch in the garage. This switch in turn connects underground to the network in the metal building.

​​I am basically working alone, with a little help from my wife, or on rare occasions from someone else such as a visiting friend, so it's going to take a while to finish the dome. Plus I can't go any faster than funds allow.
I don't have detailed drawings or an actual assembly manual from the factory for the metal dome, so the base ring was assembled to confirm accurate dimensions for drawing up the building and wheel base. This dome appears to be based on an Ash dome, and I do have a copy of an Ash dome manual for reference, which is very helpful.
I found a used steel pier listed on AstroMart that was only about an hour-and-a-half's drive from my house. It's 10" in diameter, a minimum 39" tall, but is adjustable to about 42", and has a 13" diameter top plate. ​The tube is 3/8" thick and the top, bottom and adapter plates, plus the ribs, are all 1/4" thick. It's perfect for my needs.
On the topic of AstroMart, I no longer buy equipment on their website after my account was deleted without explanation. I tried contacting the admins but they would not answer my emails. I've also read many other people's tales of similar things happening to them. Over the years I purchased a lot of astro gear on their site, but I have little patience for such unprofessional behavior. In the future, if I need a piece of gear I'll use a site like Cloudy Nights Classifieds instead.
Summer 2023 was almost over before finally making some progress on the new observatory building. Power and Internet cables were run out to the field in conjunction with running a new water line from our well to the garden beside the new garage.

Electrical power and a CAT5e cable were also trenched in from the lab building to the new garage where an Ethernet switch will connect the observatory into the lab's network.
The beginning of a hole for the pier was dug by the backhoe. I finished digging it down to solid rock by hand, in preparation for pouring the concrete base.

​The ground on this site is thin soil and clay over layers of shale rock. The soil and clay are about a foot thick and then transitions to layers of shale. The bottom in the photo is a thick horizontal bedrock layer of shale at around 2-1/2 feet deep.
A reinforced concrete pad was poured on top of the shale, and 10" concrete block form the 26" square pier base. The block will be filled with concrete to make a solid base, and a concrete top with four J-bolts set into it will allow mounting the steel pier.
The area around the pier was leveled with excess shale in preparation for digging a circular foundation trench for the concrete footer. Another row or two of block will be added onto the pier base to bring it up to to its final level.
The evening when I was finishing up around the pier base, I just happened to look up towards the western sky in time to see a long train of what I presume are Starlink satellites marching across the sky from west to east. I lost count but there had to be at least 16 visible during the time I was watching. I even had time to walk back to the house and get my wife to come out and see the parade.
After letting the shale settle a few weeks we've started digging the footers. This work is all being dug by hand because it would not be cost effective to bring back the backhoe for one small job, and there's no money in the budget for it anyway. My wife even came out and helped dig some. This photo is the first day's work. Also, a row of block has been added to the pier base.
Digging the footer deep enough in the shale by hand turned out to be a lot more work than I bargained for. It's tough going digging up multiple thinner layers of shale with a shovel and mattock, and it made me wish I could've called that backhoe back again. Leftover cutoffs of cattle panels from another job were laid down as rebar for the footer.
The footer used 26 80lb bags of ready mix concrete totaling 2080 lbs. No wonder my back hurts. Next is laying the block foundation, something I've never actually done before. Work has slowed down because we've had wet and cold days to contend with, and the little guy brought home the latest illness going around school, so I was down sick for several days, too. But there are still a few nice days in the forecast to hopefully finish the foundation before the real cold weather arrives.
Getting started on the foundation. After a couple days work the first two rows of blocks are done, which gets the foundation up to ground level. I just have to go back around and fill the joints between the top row of blocks after the mortar sets up. Then I'll switch to 8" split-face block, which match the house foundation, to lay the top two rows that are above ground. I'll keep at it as long as the weather holds.
The outside diameter of the block foundation is 12-feet 2-inches and it takes exactly 26 concrete blocks per row. The finished foundation will be four rows high.
More rain has come and gone, and there's a couple of decent days forecast, so I worked all day on a Saturday laying block again and managed to get the final two rows done, except I ran short of blocks. Now I need to drive 3+ hours round trip to the block company to pick up five more spilt-face blocks.
The entrance to the observatory will be on the southeast side and will extend below floor level to allow for a taller door. On the inside will be a couple of steps up to a wooden floor.
It took a few days to get to the block distributor, and another big rain storm came through, but I finally got the 5 missing blocks and finished the top row. Other than filling in some more joints I can now work on the entry way.
The weather was very cold for more than a week and the ground started freezing up, but now we're getting a few warmer days and it's thawing again, so I've been able to fill in around the block with gravel, and dig and pour a footer for the entry. There's still a warm day or two coming with temps above freezing at night, and I hope to finish putting mortar in all the block joints, too.
Another nice Saturday and I worked almost all day mixing mortar and finishing the joints, which took two and a half 80lb bags of ready mix. It was done and covered before it rained again that night.

My Australian shepard thinks he's my supervisor. He doesn't do any work, but he watches over everything I do.
Fortunately, we've had several more warm days which allowed me to set the blocks for the entry way, fill the center with gravel, and cut up some more scrap cattle panel to use as rebar. I leveled the wooden form around the blocks and all that's left to do is pour the concrete floor.
With the help of my little Kubota tractor I removed all the excess dirt from around the foundation and raked it smooth by hand in just one afternoon. This job would have taken me most of a week using only a shovel and wheel barrow.
The entry way floor is poured and setting. This may be the last concrete work I get done this year due to the cold weather.
More rain and snow was forecast, but before it arrived five wheel barrow loads of excess dirt and rock were removed inside the foundation. Then after the weather moved on, a vapor barrier and a layer of gravel were put down.
I'm trying to get the floor finished, but we've got more rain coming at the end of the week. During the summer heat we were lucky if it rained once a month.

All the pieces of the sill plate and outer band of the floor have been cut. The individual mating sections of band and sill have been screwed together and drilled for J-bolt anchors.

We got a few days and nights of above freezing temperatures with the rain, so the J-bolts were cemented in place and then everything was tarped over to keep it dry. After the rain passes I'll get back to working on the floor.
Rain, rain, rain. The ground is now like a sponge full of water. A layer of gravel was added around the outside of the foundation to keep the mud down, but now everything is tarped over and waiting on spring.

As far as the foundation goes, all of the cement work is done. The top of the concrete pier still needs to be poured, but first I need to confirm where the horizon line will be before I can finish it.
At some point I will also pour a small slab in front of the entry door, but that can wait for Spring, too.

​​At least now I'll have time to play frisby with the supervisor.
The rain finally let up and the occasional partly sunny day with temps in the 40's gave me a chance to work on the floor some more, but it's finally started snowing and winter is here in earnest, so all work is at a standstill until next spring.
It's now Spring 2024 and I'm back on the observatory finishing up the floor. I also added one last row of block to the pier base, which brings it up to about an inch under the subfloor. With the subfloor finished the base plate for the walls is going down and the walls will start going up very soon.
It has been so hot since about mid-June that I've gotten very little done outside. It's been well over 90°+ nearly every day here, with the heat index hitting 106° to 108°, and I'm getting too old to fry out there in that heat all day. But we finally did get a day under 90° (only 89°), with some clouds for shade, so I got the wall studs up and the doorway framed.
The walls are 48-1/2" tall, and the initial framing of the door is 70-1/2" high, but the final framing, and the door, may be a little shorter. I'm 77" tall so I'll still have to duck, but at least I won't have to crawl through a hatch.
Working mostly in the evenings, when the sweltering temps had cooled down a little, I finished adding the spacers at the top and center of the studs, plus I completed the top plate for mounting the rollers. It was cut in segments from sheets of 3/4" plywood. It's 1-1/2" thick and consists of two layers glued and screwed together. I went ahead and painted it black to help waterproof it in case it got rained on while assembling the dome.
While installing the ring I had to readjust some of the studs to get the building as circular as possible. That also meant recutting some of the spacer blocks, but it's all done now, and ready for plywood on the exterior.
Wrapping the 1/4” plywood around the building took an extra set of hands to hold each sheet in place and bend it around the structure's curve. I think wrestling an octopus might have been easier, but now my 26-sided building is officially round.
Nineteen 1/2” bolts located between the dome rollers anchor the wheel ring to the top of the building walls, plus four 1/2" threaded rods extend down the walls and connect to J-bolts in the block foundation, to further anchor the ring directly to the foundation. One of the rods is shown in the photo. We have in the past few years had thunderstorm winds of 60MPH or possibly greater, so the dome must be anchored securely.
The 23 dome roller mounts are equally spaced on the wall's wheel ring. Four 1/4” stainless steel bolts are used to secure each wheel mount. Each mount is greased before the wheel is inserted. The wheels are 3" diameter polypropylene with sealed bearings and stainless steel shafts.

​I temporarily screwed the wheel mounts in place to check the spacing of both the wheels and the ring bolts.
Once all the spacings were checked, the bolt holes for the wall ring were drilled and the bolts installed. Now I can drill holes for the wheel mount bolts and install those.
A section of the dome's base ring was slid onto the wheels to check spacing between the base and the wall ring. So far so good. Also, a vapor barrier was installed on the plywood wall in preparation for installing the metal siding.
In contrast to installing the plywood, screwing down the metal siding is a little simpler. The most time consuming tasks are trimming pieces to size, and measuring and marking screw holes so the finished siding screwheads looks nice and straight. This siding is actually leftover roofing from the log home we sold before moving. It's been laying around for the last five years so it has some scratches, but it saved me money.
The building is not completely finished, but is at a point where construction of the dome itself can begin. A lot of the interior work can't be completed anyway until the dome is finished and the building weather-tight.

​Dome construction is on a separate page. Click the link above or browse to it through the menu.
I need to get the observatory closed up so the next task was an entry door. The door was built from scratch rather than buying one and trying to cut it down to fit. It's approximately 69" tall and 31" wide. I still need to install a door knob and dead bolt.
While waiting to get missing parts made for the dome's shutter tracks, I have time to finish the pier before the weather gets cold. First I filled the base with concrete so I can pour the top riser with the j-bolts for mounting the metal pier. The overall depth of the block base is about four feet.

The square concrete top on the blocks will be flush with the top of the subfloor. Rebar was also added, plus I added a flexible conduit from the riser top that exits the side of the pier under the floor. The metal pier does not have holes for routing cables through it so the conduit will be near the edge of its base.
The round riser on the pier needs to be 7.5" tall to bring the EQ-8 mount up to the horizon line, which is 60.5" as measured from the floor to the bottom edge of the dome aperture.

The riser was made using a cut-off round plastic planter from Tractor Supply as a form. I used a round form because I didn't want square corners protruding above the floor, creating a trip hazard, plus the riser above the floor doesn't have to be as large as the block base. Also the planter adds a nice curved taper to the sides.
The forms are off and a thin coating of cement has been brushed on to fill any air holes or other defects. For safety, I'll leave the OSB bolt template on until I'm ready to permanently mount the metal pier after the concrete sets up for a week or two.

Now that the plywood forms are removed, an air gap is visible between the floor and the pier, which prevents building vibrations being transmitted into the pier.
In summary, the pier base is made from 20 each 10" concrete blocks weighing around 50-lbs per block, plus 12 each 80-lb bags of ready-mix concrete, and then there's mortar and rebar, which means the finished pier weighs in at around 2000-lbs, or 1 ton. It's sitting on a reinforced concrete pad that was poured on top of bedrock, so it should be quite stable.
I guesstimate the metal pier weighs somewhere between 150 to 200 lbs. It's much too heavy for me to pick up and set on the pier bolts, so I lifted it into position using a chain hoist. Everything lined up nicely and it dropped right into place.

​The pier is now complete. I still have to customize the top plate in order to mount the EQ-8, but I'm not ready to install it just yet.
Before continuing with finishing out the interior, I'm framing in the railing around the stairwell. I don't want anyone accidentally falling off the edge, not that I would do anything like that. Let's change the subject.

All the materials for the railing are leftovers from building the rear deck on our home a couple of years ago. I have a stack of leftovers and cut offs from various other projects around the place, which helps save money.
Next I had to fix a problem under the floor before it gets too cold to pour concrete. I originally put down a vapor barrier inside the block foundation and covered it with gravel before building the raised floor, but I knew in the back of my head that I really should have poured concrete. I was trying to save money and already had the gravel, but it came back to haunt me.

The supervisor (my Australian Shepard) liked to lay under the floor, chilling out on those nearly 100° days, while I was sweating away above deck. He decided to get even cooler by proceeding to dig up the gravel and shred the vapor barrier while I wasn't looking.
​So, I cut open a section of the floor for better access down under, and raked out the gravel. I trimmed up the vapor barrier and put down new pieces where he shredded it. Then I laid in cut up pieces of cattle panel for rebar and poured concrete. I had to buy another fifteen 80-lb bags of ready mix. It was a literal pain pouring it under that low floor, but it's done now.
I've finished up the entryway and built an open set of stairs that are easy to clean under, and harbor no hidden spaces for creepy crawlies to call home. I also added a door threshold and installed panels between the elevated floor and concrete pad. A vent was inserted to still allow for air circulation.
I want to close up the walls but first I need to install insulation and run wiring for two light switches next to the stairs. I'm using reflective bubble insulation because I already have it on hand, and I don't have to spend more money.
I installed 1/8" luan plywood on the interior walls because it is easy to bend. It was screwed on so it can be removed if anything else ever needs to be run inside the walls.

All the plywood is on except a small panel where cables come and go from under the floor. It's still open because more wiring to the pier has to be installed.

And, since the walls are curved I built a curved work table that fits flush with the wall, thereby taking up less floor space.
The interior of the dome building is basically finished. I will also add a black rubber floor, but not until I remove the ladders needed for working on the dome aperture.

​The walls have been painted in a color I call "Star Chart Blue", but Benjamin Moore calls it New York something. It looks much better than just flat black. Also, the handrails and steps were coated with Australian Timber Oil.
​Now I can start working on such things as the dome azimuth drive mount, the interconnecting contacts between the dome and building (for the shutter drive motor and aperture door actuators), and wiring the pier with DC power and a USB connection. All these projects will be on the "Automating The Dome" page.
Page created 7/24/2022
​Last edited 12/22/2024