
The pier assembly is four 4x4s bonded with construction adhesive and lagged together at two points in two directions. The top plate is three sheets of 3/4 plywood, fastened with the rest of the construction adhesive.

Here’s the location. Note the perfectly good, yet doomed, dogwood cowering over the work site. This tree was all rotted out at the base and limbs when we moved in. Yet here it fluorishes, 16 years later. Note also the picket fence, which will hopefully be taller than the finished observabox.
The hole was about 45 inches deep when I stopped. Hard to go much deeper. Actually, digging the hole was surprisingly easy. I actually thought about renting a posthole digger, but I realized I would do far more harm to my back getting the digger in and out of my car than simply digging the hole myself. My yard is notorious for big quartz rocks, but there were none in the hole. An auspicious start. I put some gravel and a large rock at the bottom as the “footer†for the pier.

Here’s where it got tricky. My single top plate approach minimizes the height of the assembly, but requires an atypical attachment. I used 3/8" x 4" hanger bolts, which are screw threaded on one end and machine threaded on the other. I ratcheted them in by putting three nuts and a washer together. Then I drilled the top plate, with a recess for each hanger bolt to hold a nut and washer. I’ll tool the top plate tomorrow for my Celestron wedge.

And here is the “pier,†all eight inches of it, with the last bag of cement poured in just after dusk. There was only one D’OH! moment. It was when I discovered that, despite carefully taking magnetic declination into account, my pier was lined up 15 degrees off true north. Remember how some folks note that steel can throw off a compass? D’oh! I don’t think it matters, since I won’t be tooling the top plate until I can line up on Polaris anyway. It will just look a bit odd. If that’s the worst that happens with this project, I’m golden.
Advice is welcome!
- Kevin