The Practical Observatory #3
by Dennis Allen

It seems that people joining our astronomy club recently have their own Schmidt-Cassegrain telescopes. With the rather long setup time of a SCT, we saw a need to start providing permanent piers at our facility.

As part of an overall site plan, our club decided to pour two new viewing pads on our upper hill. The west pad would be 10' by 20' and have two permanent piers, the east pad would be 10' by 14' and have one permanent pier. On the west pad we would construct a small 8' by 8' building to house one pier. If successful, we'll construct a twin building on the east pad to house the second pier. The third pier will hide in the west pad concrete until needed.

The Observatory Design

We mulled over a couple of designs, including several variations of a roll-off roof. Finally, the head of our site improvement committee came up with a unique design. The roof will be a standard peak running north-south. This roof, however, will split at the top. As you can see in his design drawing, the two roof sections have swivel arms which rotate on 1-1/2" steel shafts connected to bearings on the north and south walls. The two roof sections, therefore, pivot east and west. On the ground, each section would only make a 4' footprint. To make such a design possible, the head of our site improvement committee will fabricate the swivel hardware and permanent pier in his work shop.

As you can see in this illustration, the permanent pier is in the middle of the 8' by 8' building. The walls are 4' high and the north wall has a 3' wide door. We figured to use whole sheets of 7/16" particle plywood for the 4' walls. We plan to make the door out of 2"-by-4" and 7/16" plywood. Since the roof sections will pivot away, there's no need for an upper door.

The First Work Party

For our first work party, we dug forms for the two concrete pads. We had six pieces of 10' 2" by 4" studs, four pieces of 12' studs, plus scrap wood for stakes. We dug and screened the 10' (starts at 10' and widens to 14') by 20' west pad and the 10' by 14' east pad. We also had to bury three 18" by 3.5' sono tubes for the permanent piers. To save on concrete, we filled half the tubes with concrete core blocks we had laying around. Altogether, we figured we'd need six yards of concrete.

The Second Work Party

For our second work party, we floated concrete. We ordered 6.5 yards of fiber-mix concrete. We used 15' of separator strips (store didn't have zip strips), a 10' piece of 2" PVC, three 2" 90 degree PVC elbows, and a couple of 2" PVC connectors. The PVC is conduit for the electrical and two cat5 lines (one for Internet and one for USB) to the three piers. Also brought 25 6" anchor bolts for the new building and two of the three sono tubes.

The head of our site improvement committee already made a test pier, so we used it's base to make a couple of wooden templates. We'll use these templates to drop in the anchor bolts for the piers.

We figured there might be leftover cement, so we started digging another form. Got a 6' wide section dug before the cement truck arrived. By then we had enough members present to start pouring. We were fortunate to have someone who knew cement, so we had the west and east pads poured and floated in no time. We stuck in the anchor bolts for the west building and two of the piers. After a half hour, we broomed the pads.

A club member brought a fourth sono tube for his 4" pipe pier. Had to hustle to dig out the sono tube in the 6' section. And it took time to drill out holes in the pipe pier for a couple of rebar rods. Fortunately, the cement hauler was patient and waited until we were ready. By the time the fourth pier was poured, we had about half a yard leftover cement.

The Third Work Party

Before the work party, the lumberyard brought out material for the walls. We started by caulking and bolting down treated stubs to the concrete. We cut 42" studs for the 4' walls. Two walls were 96" wide, all were standard 16" centers. Once we nailed the stub frames to the treated stubs we added another layer of overlapping stub on top. Then we nailed four sheets of 7/16" particle plywood to the walls. To accommodate the design, we cut a 4' section out of the north wall and made a 4' door out of 2" by 4" studs laid flat and 7/16" plywood.

The Fourth Work Party.

For the fourth work party, we put up the vinyl siding.  We used 4"x1" cedar rough-cut strips for all the wall edges. The bottom of each wall has a vinyl starter strip, the sides and top of each wall has j-channel. Once all the trim was hung, the siding went up fast.

The August Work Parties

At the fifth work party, we got the two roof sections built. Each section has five purlins, covered by corrugated sheet metal. Except for the north/south gables, there are no trusses. The gables extend past the north/south walls a couple of inches and overhang the north/south walls a couple of inches. This made room for the swivel brackets. The roofing cap is secured to the west roof section. So to close the building you must first raise the east roof section, then the west roof section.

On the next work party we finished the gable siding and hung the door.  Also got the building wired for electricity.

On the last Saturday in August we got the swivel hardware installed. The swivel brackets installed under the north/south gables. The 1-1/2" steel shafts are set screwed to the swivel brackets. Inside the building are heavy duty plates with bearings for the steel shafts.

In addition to the swivel hardware, the head of our site improvement committee also made a new permanent pier. This pier is smaller than the first one he made, allowing the telescope to remain on the pier when the building is closed.

We've spent the last couple of days trying to finish the building. We put latches on the inside of the north/south gables to secure the roof sections. Installed a set of garage-door handles on the outside of each roof section, so you have something to grab when lowering a roof section.

To keep the roofing cap from flapping in the wind, we added gussets to the west roof section. Spent time taping a new mounting plate, to secure the LX-200 wedge to the permanent pier. Also spent time framing the door, installing a door threshold, and installing a deadbolt lock. We just put in a new 100 amp electrical box in the storage building, so the new building could have electricity.

The September Work Parties

We spent September adding finishing touches. Got the lights installed, the building and pier are both wired. Installed the N.E./N.W. corner tables and East bench. To give the building a real finished look, we paneled the inside with 4" cedar strips.

To make the roof sections easier to open and close, each section has two garage door springs and cable system. Different size springs were tried until we got each section to balance out. Now each roof section can be raised and lowered with one hand.

To cover the sharp edges of the corrugated roof, we installed sheet metal j-channel. On the bottom j-channel, we drilled holes to allow water to drain. Here it is, not three months since we started and the building is complete and occupied.

Conclusion

Considering the complexity, I'm pleased on how quickly the building went up. While there are many club members who contributed their time and sweat to this project, a few do need special acknowledgement: Mark Mikula, our Vice President, who spent the most time and money to this project. Jim Malda, former President and head of our site improvement committee. Without his design skills or his work shop, we simply couldn't have built a split-roof building. Rick Andrews, who did all of the electrical work. I could take some credit, but modesty forbids. Special thanks to Jim Rotman of the Muskegon Community College, who donated our concrete. Ryan Edson, who help poured the concrete. And Baker Lumber, who help out tremendously on the material.

Future Events

Since the concrete was poured, we've had another design change. A request for the next building to go up next to this building, on the west pad. Now we have the hidden third concrete pier, but the west pad is only 10' wide in that area. Not enough room for an 8' square building and a 4' sidewalk. To accommodate this request, the county wastewater system graciously donated fill sand so we could expand our upper hill south. And the local community college has offered to spread the dirt. So now all we need to do is to add a 2' by 8' section of concrete to the west pad and we can begin building #2.

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