The observatory build starts next Monday!!  Today I’ve found a major flaw in my plan, but I see it as an opportunity to try something different rather than a show stopper. The plan is to fit the flat plate from the top of the tripod into the depression in a brake disk,  weld the pieces together and bolt the whole lot to the top of a concrete pillar.  I had said I’d build a column form but having looked at my warped timbers I decided to buy a 300mm (outside diameter) x 1 metre tube to cast the column and I found some 10mm brake disks in the bargain bucket at Halfords for £10. I bought M20 threaded bar to sink into the column onto which the disk will fit.  Did you spot the flaw? The piece from the top of the tripod is not steel as I expected but is instead a non-ferous alloy of as yet undermined metals. I have an arc welder, my brother has a mig welder but neither of these will weld alloy to steel!

Putting this minor distraction to one side, the column form will be held in place with a wooden cage (I’ve made that) which will sit on wooden beams laid across the base pit.  The pit will be approx 900mm cubed with the column rising from the centre. I’ll level the cage by driving timbers into the ground at angles then screwing them to the cage to hold it upright. This will have to be done on the day of the concrete pour to make sure everything is as perfect as I can get it. When the concrete is set I’ll build my self-assembly steel shed around the column. I’ll build a wooden frame inside the shed extending to the rear to allow the roof to be slid off.  I’ve found a few examples of this being done online but my favourite, and the one I’m using as inspiration is the Linnhe Observatory in Scotland.

Rather than cast a concrete floor I’ll be laying a waterproof membrane and building a raised wooden floor. The observatory will be for the most part remotely operated so there’s no need to build in creature comforts however I will be including storage for all the astro odds and ends that I’ve collected.

I’ll update this as the project progresses …

A view of the column top. The wooden plate will be removed after the concrete has set leaving a spanner sized gap for tightening the bolt that will hold the EQ6 in place.

This is the tripod top sitting perfectly in the brake-disk. If only I could weld it there. Plan B may involve drilling in from the sides and bolting the two pieces together. Unless I can find someone with a tig welder?