Black Oak Observatory Construction

Welcome to a gallery narrating my astronomical observatory construction. Entries will be added in chronological sequence. Click on photos for a larger view. Schematic plans and detail drawings are available here.

foundationframingfinish


July 11




 

Whereupon we enter the finish: a labyrinthean and vexed journey of details and niggles.

First thing, we put the plywood onto the framed roof, and Bob trimmed the outside edges. We then decided it would be better to put up the corrugated metal before raising the roof section on its casters. Unfortunately I realized we needed the galvanized flashing to trim the roof, and did not have it, nor the necessary tar paper. Mead Clark required a week to get the flashing, which I ordered on Friday July 8. I stopped by to pick up the order, Bob took Friday off.

Reliable Hardware had called Wednesday to report the two telescope piers were finished, so after surfacing the roof we went to pick them up. Both were completed to spec. There was a 5' piece of tube steel left over, which Bob was eager to sell for scrap — "That piece might be worth $160!" We took it to Bataeff Salvage, had it weighed ... and got $13.50 for it. I split the windfall with Bob as promised, and we went to Mead Clark to pick up redwood trellis materials.

Once home, we unloaded the piers and lumber. I cleaned the exterior of the piers with acetone and applied a coat of iron oxide primer, as Bob recommended. It was too windy to use a sprayer Bob left for the application, but the brushed texture helped to minimize the texture of the pitted metal. I liked the chocolate brown effect, but not enough to change my preference for black.

Saturday I also took advantage of a cool morning to level the telescope pier caissons with grout. I mixed up a full bag with enough water to create a "liquid" consistency. I was under the impression that this was leveling grout, which would flow out like cream to make a perfectly level surface. It was not. Instead, the "liquid" grout had a slushy consistency that would not flow. Agh!

Once I realized the problem, I went to the garage for two 1/4" plywood disks that I had already cut to serve as vibration dampening bases for the piers. I placed these over a sheet of aluminum foil and pressed them down over their respective piers, then used a torpedo level to set them, scooping excess grout around their circumference and out the hole moulded into the caisson for electrical connections.

I spent the rest of Saturday day drilling out the four pier top plate holes for the threaded rod supports on the leveling plates. I had spec'd 5/8" holes for 5/8" rods, which created a tight and scraping fit — my bad. I used an 11/16" drill to widen the holes sufficiently, then used a Dremel grinder and rat tail file to elongate one hole to receive an off center rod. Then I painted both piers in satin black.

Sunday I cut away the sonotube and examined the grouted caissons. The south caisson finished off nicely, smooth and level despite a few bubbles, but the north caisson is somewhat uneven; the plywood leveling disk warped or bent slightly for some reason. However I discovered that the grout is easy to sculpt with a wood rasp or grinder, so I cleaned up the edges, electrical holes, and dripped grout underfloor. I also uncovered a working section of the existing garden conduit that will be spliced into to provide the observatory power.

Monday Bob arrived to finish the trellis spanning two roof track support posts, which my wife will use to tendril some camouflaging vines along the side of the observatory visible from our residence. He then took off for another job, and came by later with tar paper and caulk to install the corrugated roof.

I was off on separate errands, returning defective light fixtures. I spent Monday afteroon putting primer on our final lumber pieces. I stacked all the painted lumber along the sides of the structure and picked up all the stray bits of cut wood and plywood used to paint the lumber on the grass. Everything is ready for trenching the conduit line on Tuesday, and putting metal on the roof.


July 12

Today was trench day. Bob rented and delivered the trencher, drove it down below the studio and around the field. I had the concept to start at the observatory and work uphill to the existing conduit, lift the blade and back away. But Bob preferred to start at the top and back down, then turn the trencher over the trench to finish the cut going uphill, then drive it over the trench to leave.

After he returned the trencher, we started the process of installing the corrugated metal roofing. The tar paper went on without a hitch, but then things went haywire. Something with wiggle strips, something with caulk, the panels didn't fit the strips, the crucial top strip wasn't stapled down and squirmed out of place, Bob tried poking it back in with a stick ... I asked him to stop work so that I could check with the corrugated metal vendor on the best installation procedure.

Well ... maybe we'll have that roof on its casters by Thursday. Tomorrow is the electrician.

 

July 13

 

Today was electrical. Aaron of Spyrka Electric arrived promptly at 7am and got straight to work.

We briefly confirmed the particulars of the install, and he told me what would best serve as backing for the outlet, fixture and switch boxes. I cut the braces from scrap 2x6, nailed them in place, primed them, and took my wife to pick up her car at the garage.

All wiring is in gray PVC conduit, to protect against insects and gnawing vermin. All fixtures are outdoor grade, which means that I can (as Aaron put it) "hose them down" without problems.

The circuit box can handle expansion circuits, for example if I decide later to install garage door openers to open and close the observatory roof.

Toward sunset, as the air cooled down, I filled in the trench and set the Christy boxes. They will be partly covered by paving stones, accessible but otherwise unobtrusive.

Nice to have a productive day. All that remains is to get the roof finished, the piers mounted, and the door installed, and the observatory will be ready for operation.

Installing the flooring, constructing the entry platform, finishing the interior painting, setting pathway pavers, and building the large storage cabinet are piecework tasks that I can finish at my leisure.


July 14

Today, finally, the south roof went on the rails.

I started the morning pulling off all the foam wiggle moulding so we could just lay the corrugated metal sheets. An hour and four sheets later, the roof was covered, and we started on the process of raising it onto the rails.

My original concept was to bare frame the roof, lift the frame up onto blocks, then complete construction. Bob preferred to work with the roof down, then raise the completed structure with jacks — probably the most prudent way to work.

Using two 20 ton capacity car jacks and two 5' posts, we lifted the low (south) side of the roof away from the rail plate and blocked it in place with lumber. Raised on a 6x6" block and three stacked 2x6" remants, it was high enough for Bob to drill out the caster bolt holes with a lateral drill and mount the casters on their rail.

We then lowered the mounted casters to about 1" above the rail plate, slid an angle steel track underneath, and let the roof down. The casters dropped crisply onto the edge.

We did the same on the high (north) side, and when the roof was "on all fours" we wedged it with a length of 2x4" redwood and scrap blocks to prevent it from rolling off the tracks.

The final step: we'll roll the roof out onto the exterior track supports, to ensure the rails are spaced in perfect parallel, precisely move the track ends at the observatory center so that they are symmetrically placed on the rail plates, secure the ends; roll the roof back to the center position, recenter the rails, check fit by rolling the roof back and forth a few times, and finally secure the track along its length with lag bolts.

Friday we'll begin framing the other half of the roof.

 


July 15

 

Today we framed the north half of the roof, including the plywood subroof.

We followed the same measurements and procedures as we did for the south half. Unfortunately we ran into lumber delays, miscut pieces and splintered dry wood, which slowed down progress. But we finished as planned and in good spirits.

This weekend I will finish painting the steel piers and fill them with foam insulation (to dampen any vibration), and probably choose the flooring material.

We also confirmed the south roof was rolling properly on its angle steel tracks, and that we could adjust the location of the rails by moving the roof from one end to the other. We'll wait until both roof halves are completed so that we can align them together.


July 19

Today we mounted casters on the north half of the roof and got it up on the angle steel rails. This concluded the heavy lifting, possibly won't go right steps of the construction.

We discovered that one of the outboard beams on the south side was skewed, atop a post that was no longer plumb. As we'd plumbed and centered it pretty carefully before it was braced, we're left either with shrinking warping lumber or shifting in the entire structure as an explanation. Anyway, we untacked the brace, plumbed the post, and moved on.

Once both halves were up we shimmied the rails into better position, moving the roof from one end of the rails to the other to straighten and align them. We finished with the north roof perfectly flush with the north wall when the roof is closed, the south roof perfectly aligned with the sides of the north roof, and the south roof skewed to the south wall by about 1/4". We'll just shim the south "skirt" of T1-11 and call it good.

Phil stopped by with his heavy duty cargo dolly that we will use to install the telescope piers tomorrow. We're done with construction inside the structure; the piers, door and flooring are all that remain.

Below is a southwest panorama from the observatory door, with the roof open. I'll have clear visibility down to about –45° celestial latitude — all of Scorpius and Sagittarius, much of Centaurus and most of Puppis.

 


July 20

 

Despite the heat, Bob got the second half of the roof covered in tarpaper and corrugated metal. To do this, he trimmed the roof plywood on all four sides, including the "seam" down the middle of the building. To get the seam right, he mounted the "skirt" on the south edge of the south roof, which limits the travel of the roof in the closed position.

As the picture shows, the skirt extends below the top of the roof by about 6 inches, and will be finished with 1x4" cedar trim. This provides a strong and watertight seal on the north and south sides. The east and west sides will be trimmed in a similar way, mounted on a 1x12" plank (leaning against the side of the building) for extra support. Note that the bracing blocks below the roof have been mounted horizontally, to accommodate cutouts in the skirts if more ventilation seems desirable.

The weather was hot so Bob left early. Later Phil came by and using his industrial grade dolly we wrestled the two telescope piers from the garage down the gravel path behind the residence and down the gopher scarred field and up two planks into the observatory. Setting the pier on the tips of the threaded rods, carefully walking it into position allowed the pier to drop nicely onto the caisson. After I adjusted the pier leveling plates, Phil helped me carry down the Meade scope and bolt it in place, and after he left I brought down the Losmandy mount for the 10" Royce Dall Kirkham scope.

The photos show the finished piers and equipment ... the Meade scope is going through its orientation exercises.

Phil came back in the evening and we had a couple of hours of "first light" viewing. The seeing at the new site seems significantly better than up on the driveway by the residence, and we had some great views of low altitude globular clusters in Scorpius and Sagittarius, and my first view of M7.

 


July 21

Another short day, due to the heat. Bob installed the door and built a handsome redwood landing on the concrete pad. At last, no more tripping over the embedded threaded rods!

Sophie naturally has to make a thorough inspection.

 

July 23

 

Friday Jan and I spent the day in San Francisco, and Bob had the day off.

The weekend turned dreary and seemed likely to rain. Rather than wait for Bob, I finished installing the "skirts" on the open two sides of the roof. These will be trimmed with the same 1x4" cedar that is on the corners of the building.

I also replaced the hose roof rollstops with short lengths of 1/2" black nylon rope — stronger and also less visible. The ends were singed with a gas stove burner, then rolled on a granite counter, to fuse them against unraveling.


July 25

Today Bob came over and finished up some details with the exterior "skirts" and the door installation.

There is still the installation of a linoleum floor, a storage cabinet and some weatherstripping and possible ventilation tweaks to do, but those details aside the observatory is finally finished and fully operational.

I've had several nights of observing in it and the design meets all my expectations. The roof operates flawlessly, the walls create minimal obstruction to the southern horizon and nicely block lights from the residence. The space is comfortable and functional without being cramped. There is plenty of room for a storage cabinet and a couple of chairs.

 

August 2

 

A slow week ... as soon as the observatory was completed, a cool evening fog began spreading over the sky each evening: the stars were completely blotted from view. It's been like that for the past week.

Yesterday I went to the floor covering store. Turns out that linoleum or vinyl type products require an adhesive that breaks down if exposed to cold; Phil says he has to replace his tiles periodically. Instead I arranged for underlayment and indoor/outdoor carpeting to be installed in the observatory. The color is mineral twist, a very dark yellow green with flecks of random color. It seemed least likely to show dust or fading. It will also provide a slight cushion to accidentally dropped equipment.

Today I spent the afternoon cutting three 4'x8' sheets of 3/4" oak plywood into the various pieces necessary for the oak storage cabinet. I had to use a skillsaw and two aluminum sawhorses, but the work turned out very satisfactory. It will be assembled in place after the carpeting is installed.

Tomorrow Bob comes by with a helper and cleans up the trash, scraps, paint cans and fraff that litter the site. Then I set to work laying the paving stone path to the observatory door.


August 23

A week or two of waiting for the carpet to be shipped from the manufacturer in Alabama.

Today the installers showed up around 9am and were finished installing the 3/8" plywood underlayment and carpet by noon. They did excellent work; the two cuts required to wrap the carpet around the two piers were closed up without a trace, and the installer took extra care to tuck the edges down around the pier holes.

I like the contrast with the white walls, and the carpet is more comfortable than the hard plywood under foot. It is just enough cushion to save a dropped eyepiece from damage.

 

August 25

With the carpet installed, I brought down the pieces of the cabinet and assembled it in place using nails and glue. This took two days, as some of the shelves had to be tweaked to fit properly and glue joints left overnight to cure. Edges were rounded with a file and hinges and magnetic clasps installed.

The cabinet divides into a storage area on the left and a study area on the right. The storage area with two doors can take four eyepiece cases, optical and mount accessories, lens cleaning materials, and so on.

The work area includes shelves for books and a desk area with an overhead fluorescent light fixture for consulting printed materials or adjusting fine parts. The desk is supported underneath by an oversize atlas storage shelf. The desk folds up when not in use to keep it out of the way, and in that position the atlas storage area is protected by a slide in piece of plywood.

I bought two different kinds of handles for the storage doors, then decided to leave them off — nothing to snag clothing or bump into in the dark. I routered a small groove along the outside edges so the doors can be grasped with the fingers.

As earthquake protection, two lag bolts secure the 3/4" back panel to two studs in the wall behind.

The top of the cabinet is about 2 feet below the rafters of the rolling roof, and provides almost 6 square feet of storage surface for tool boxes, tarps, and a small vacuum cleaner.


September 1

And to conclude ... today I installed the "scope bunk", constructed of 2' x 4' fir sections that I precut yesterday.

The design is fairly evident from the photo: 2' x 4' fir boards are nailed to the south and west wall studs and nailed together at a single 43" high upright. Two telescopes with tube diameters from 12" to 14" and lengths up to 60" (ƒ/5 in a 12" Newtonian, including focuser) can be stored between the parallel boards set 9-1/2" apart; the upper bunk is 20" below the birch top, and the lower bunk 15" below that.

The 5/8" birch plywood top doubles as a standing desk and a 17" x 45" work area. It is bordered with strips of lath to prevent pencils, eyepieces and such from rolling off the edges and behind the bunk. Scopes removed from the mounting can be placed here for adjustments or repairs, or until another scope is installed on the mount, opening up a bunk space for the retired scope.

The AstroTech 10" ƒ/8 Ritchey-Chretien is shown in storage, with the extra space for the Royce 10" ƒ/20 Dall Kirkham still awaiting delivery. The AstroTech 10" ƒ/4 Imaging Newtonian is currently on the G11 mount.

 

 

Well, the observatory is finally finished and ready for routine use. I hope this narrative, images and the related schematic plans have given you some ideas for your own observatory, perhaps even inspired you to take the plunge.


Thanks for visiting, and clear skies!