A detailed account of the construction of Rokeby Observatory.

Genesis
	It all started with a circle in a field...
	... and a "back of the napkin" sketch.
Foundations
	Sonotube, that remarkably good friend of the observatory pier builder, turns out to be hard to find in Ireland. With the Celtic Tiger-inspired building boom, though, sewer pipes are a dime-a-dozen. (They're also socketed -- which doesn't matter to us -- but tell a site manager that you'd be happy enough with one with a busted seal and you'll get it even cheaper.)
The sewer pipe would be set about 1 foot deep in a 4 foot cube, with a steel reinforcement cage extending from the cube up to the top of the pipe. J-bolts would then be set in the top for anchoring of a steel pier for the final mounting. Since I didn't feel like digging a 4 foot cube, now seemed like a good time to get a digger man out and have a cable trench dug as well. I installed 2.5mm² three-core armoured cable, which in retrospect was too small for a 150m run. (I get a fairly significant voltage drop, particularly with a kettle plugged in. The current solution is to use a low-wattage "caravan" kettle.)
	I couldn't find anyone to supply me with rebar hoops, so I bent my own around a log. This is a lot harder than it sounds -- even 1/2" rebar is pretty stiff stuff. (Springy too; note how much larger the hoops are than the log.) I also fabricated some stainless steel J-bolts out of threaded rod.
	The finished cage. This section goes up the middle of the sewer pipe and down into the 4-foot cubic foundation. Blockwork was added to the hole to hold the pipe at the right height. Additional reinforcement bars will be tied to the central cage extending out into the cube.
Did I mention that dang pipe weighs about 1800 pounds?
	I ended up spending half a day erecting some scaffolding pipes to allow me to winch up the pipe. While I bent the crossbar fairly severly, it did work, and no one died in the process.
	Just rewards.
The Big Pour
	On the day of the big pour, we spent the morning getting ready for the concrete delivery. I ordered enough to do the 4-foot cube, after which we'd give it a few hours to firm up and then pour the pipe filling by hand. This was meant to ensure that we didn't have a cold-joint between the two, but also that the wet concrete in the pipe wouldn't just run out the bottom. The two guys with the tamping sticks are myself and a friend; my back is to the camera. The two lassies are my girls, out for a look-see.
After lunch, the race was on.  We mixed and bucketed 1m³ of concrete up the scaffolding and into the pipe in the span of about 3 hours. After that, the J-bolts were forced into the wet concrete with a plywood template on top for spacing.
The Pad
	The grass and topsoil were removed from a 10' diameter circle around the concrete pier. The top of the pier foundation was then isolated with 1/2" of styrofoam. Roofing felt was placed on top of the styrofoam to keep the hardcore from getting embedded into it. This is intended to keep any vibrations from walking around the observatory from affecting the pier (and therefore scope).
	Several tons of hardcore where then poured into the hole, raked out, and whacked. The hardcore provides both a stable platform for the concrete and more importantly, drainage of any ground or surface water from under the pad. The whacker is required to get a nice, compacted layer. You can also see the plastic pipe running from the outside, under the hardcore and up. This will be used as a cable race to feed the power line into the observatory.
Finally, a vapor barrier (polythene) was laid over the hardcore, a timber frame added to form the edge of the pad, and steel reinforcement cut to fit. (Don't cut the steel over the vapor barrier. The flying sparks will melt lots of little holes in the plastic. Trust me, I know.)
	First order of business was to place mounds of concrete strategically under the steel to support it in the middle of what will be the finish depth. Then the rest of the concrete was mixed, barrowed in, and screeded. This was a very long day (even with a friend helping out again)....
	And the finished result. We had cattle in the field at the time, so the fence went up to prevent a Hollywood-style hoof-printing session by the cows. They had spent several hours earlier licking the windshield of my car, which I thought was pretty funny until I realized that I had 1/2" of caked cow-snot stuck to my window.
Framing it Out
	The main framing will consist of two plywood rings top and bottom, with 3x2 studding in between. Cross-braces between the studs will support the floor joists. The ring sections were marked out on sheets of 1/2" WBP plywood, and then cut out with a jig-saw. We needed enough sections to make 4 complete circles.
The sections were then laminated into two rings, with two layers to each ring. This allowed us to stagger all the joints. The ring layers were glued and screwed to form a nice, cohesive unit. A gap will be cut in the bottom ring for the door, but we left it whole for now.
	We're constructing in the middle of the wet season in Ireland, and a round building is a bit fiddly. We therefore made the (very prudent, in hindsight) decision to do a test erection under a roof. Fortunately, I have a space big enough for this. First order of business was to lay out several sheets of Sterling board (OSB on the other side of the pond) and use one of the rings to rough-cut the flooring pieces.
Next we cut all the floor joists to length. There are two principal holes in the floor -- one for the telescope pier and one for the stairs. The stairs hole (in the foreground from center) will be covered with a trapdoor when not in use. We perhaps got a little carried away and mortise-and-tenoned all the flooring joints. But hey, this is a hobby, right?
	I agonized at some length over how one gets a flat door into a round building. In the end, I chose to model the "vestibule" loosely on the Grubb 10" dome at Armagh Observatory. The roof over the vestibule was quite difficult to make as the back edge is a compound curve. But after considerable fiddling we managed it.
	The stringers were marked and cut against the pre-assembled floor joists, and were then rebated for the treads. The front of the treads were rounded over, and then screwed and glued into the stringers.
Out Standing in a Field
	After all the various parts passed their trial fit, the whole kit was dragged out into the field and assembled. There was one tricky part as I didn't want to toe-screw the joists into the bottom rail. So we screwed in all the joists with the bottom ring up on blocks (so we could get under it), and then lowered it down by removing a single block from each stack as we went around (and around and around).
There's some additional bracing in this picture to keep the structure round until the outer skin goes on. While the outside will need to look like stonework to fit in with the house, I desired to reduce thermal mass as much as possible. The timber frame will therefore be clad with two layers of 1/4" WBP plywood (with staggered joints), covered with a sand-and-cement render.
	The outside edge of the pad was flashed with lead sheeting, and a vapor-barrier added to stand between the plywood and the cement render. Rib-lath (an expanded metal) was then screwed on to give the cement render a key.
	Next was the floor. I have to confess that the pre-cut pieces didn't quite fit and required a bit of trimming. Herringbone struts were also added under the floor to keep the floor joists from twisting.
	The rendered observatory, complete with a temporary "lid", awaiting its dome.
Domed
	Based on the success of the pre-assembly of the timber structure, we decided to do the same with the dome. Since we needed to drill a bunch of holes for all the bolts, it seemed like an absolutely flat floor was required, so we used the breakfast room this time around.
	I got the circular skirt with the dome (a 10' Technical Innovations HomeDome), which did a nice job of flashing the top of the rendering. Due in no small part to the pre-assembly, the dome went together quite quickly. The chap on the right is Paul, another buddy up to lend a hand. Yours truly is on the left.
	The upstairs walls were painted a dark blue to match the inside of the dome, and the downstairs a lighter blue. Both were sprayed on, but as there is no inner skin to the walls, the paint drifted down between the joists a bit. I call the effect "twilight". You can also see the wiring going in for the white (one each floor) and red (two each floor) lights. The reds are on a dimmer.
Since the stairs are softwood, I wanted a very flexible and hard-wearing paint for them. I found a blue floor paint, but of course it didn't match either of the wall blues. At this point, the only thing to do was to get a fourth blue for the door, which I did. Note the trap-door which covers the stairs when the observatory is in use.
	I had a bit of left-over countertop from another project. Coupled with some jig-sawed plywood brackets, I was able to fashion a servicable kitchenette for making tea or coffee. This is where that low-wattage kettle comes in, but this picture was taken with the "regular" unit still installed.
Equipped
	The concrete post runs up the middle of the lower floor, and a 50" tall, 10" diameter steel pier is bolted to the top of it, just below ceiling level. Those bolts are the ends of the stainless steel J-bolts inserted into the wet concrete all those many moons ago....
The pier tube is approx 1/4" thick, hot-dipped galvanized inside and out. The top and bottom plates are about 3/4" thick, and there are gussets around the bottom. The floor sections on either side of the pier are removable in case it needs to be changed out for another configuration. (Indeed, the steel pier has already been changed once when I moved from an alt-az fork mount to a GEM.)
	Here's the older, shorter pier with the Gigawedge on it.
	I use a pair of 7A (10A peak) 13.6V power supplies: one for the telescope, and one for dew heaters, fans, and my heated clothing. The power is routed under the floor and then up the pier, with a pair of cigarette lighter sockets for each. The indicator lights on the sockets were much too bright. A bit of nail-polish sorted that out.
	Later, I crafted some eyepiece racks from a polyethelyne cutting board and some custom-machined brackets.
Loaded for Bear:		Love that Green!
	Here's a must have for all you observatory hounds: I'm sure you've all discovered pneumatic chairs, and yes, they're wonderful... ... but the bees' knees is a pneumatic chair with wheels!
Finis