I have been imaging for about a year now and realizing that I would get much more out of the hobby with an observatory..... So I am going to build one in my yard with a tandem warm room to use as an office. I have built many things before, but never an observatory. The first step of course is the pier. I have gone back and forth with a cement pier vs. an expensive steel Pier (i.e. PierTech). The pier would be isolated from the observatory floor which would be a wooden floor.
I ran across these pre-cast stackable footings at a home store : https://www.ez-crete...oducts/ez-tube/
It got me to think that I could first build a concrete pad myself 24" x 24" x ~40" deep. Then I could order the stackable footing, roll the sections into the yard and set them on the pad with concrete adhesive, and stack with adhesive between each layer. The total weight of the concrete for a 52" high pier (for mostly AP) would be over 300 LBS. I would then need to drill out and add the steel plates at the top using an epoxy resin.
My concerns are 1) the base - it weighs ~125LBS. I would need to roll it to set into place. and 2) Drilling into the top section for the plate (making sure the bolts are straight).
To address your concerns:
1. Yes, the base is over 100lbs. I used a dolly to move it to where it was going to be installed. Once the hole was dug, I used the threaded rod to pick it up and put it in the hole.
2. I drilled the holes and, yes, one of them went crooked a bit. It helps to go slow and it also helps to do holes a little bigger than the bolt to give some "wiggle room". I used Sika AnchorFix to secure the bolts, but I don't remember if it was 1 or 2. Thankfully, I was able to enlarge the holes in the mounting plate to accommodate the crookedness of the bolts.
I used Sikaflex construction adhesive for the joints between the sections. It's a waterproof, weatherproof adhesive. I've not experienced any movement since I've installed the pier. The soil here is heavy clay and I compacted it every 4 inches as we filled the hole. We did go deeper than planned which made the pier a little shorter than I wanted/needed. I made up the difference by purchasing a pier extension.
My goal was to eliminate the setting up of a tripod and mount for each observing session. I wanted to be able to just take the mount out and be polar aligned close enough for visual observing. When I begin taking pictures, I will do a more precise polar alignment.
I guess I could have dug a smaller diameter hole and framed some sort of support for the above ground concrete (sonotube, PVC, etc) and then mixed a bunch of bags of concrete, or called a concrete company, and poured concrete.
That sounded like a lot of work for me. With the pre-cast pier, I just dug a hole and assembled the pieces, paying attention to plumb and square, and I was done. It was a quick and easy solution for me. But, everyone's needs are different and the pre-cast pier may not work for everyone.
About a week or so ago I was walking through the backyard, looking up at Orion. Yes, I walked right into the pier. The mount wasn't on it, just the sundial. I have a nice bruise on my upper thigh now. The next morning I checked the level of the mount plate and it's still between the bubbles.
Our plan is to decorate the column this spring to make it more attractive. We have some mosaic tiles we will put on it.
Edited by ryanr256, 23 February 2021 - 08:58 PM.