14.11.2020 Climb every mounting.

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Saturday 14th 10.45 48/47F. Early cloud clearing to watery sunshine. Thin cloud drifting slowly across the field of view. Causing a rise and fall in image brightness. The image is so dimmed that I'm not using a GPC. [Yet.]

I have an enclosure for the new PSU in the post. Plus a fuse box and multiple, blade fuses from 2-7.5A. Should all be here on Monday. These will provide a greater element of safety with the new and much more powerful PSU. 12.5A at 12V.

12.30. No useful images captured all morning. 

I examined the mounting. Looking at possible improvements and weaknesses. Having set the Dec housing horizontal I could check the balance point on the pier with a weighted loop. To my [slight] surprise I had placed the C of G very close to the centre of the large disk on which the mounting rests. There is a 16mm threaded rod holding the mounting onto the pier. This allows azimuth adjustment when required.

The C of G of the mounting and instruments falls perpendicularly from the centre of the Dec shaft where it lines up with the PA axis. The complete mounting's C of G cannot be more than 1-2 cm south of optimum. 

The disk itself is centrally placed on the pier top. So one could argue there is a very slight tendency for the pier to lean southwards over time if the concrete anchors on the south side should sink. These anchors were buried in well compacted self-compacting gravel. They haven't moved yet.

I have never had to adjust the pier "feet" height to bring the top of the pier back to the horizontal once achieved. Any error of level is still within a couple of millimetres. Given the pier's height [12' 10" or 3.93m] and the considerable weight resting on top, I think it can safely be judged successful. Though I should probably have arranged the pier to point north-south, east-west. As it is the mounting is skewed on the laminated top of the pier.

Provided no short circuits exist between the building and the pier it is well isolated against my heavy footfalls on the obs. floor as I clomp about in my huge, winter boots. 

The four, 100x100mm [4"x4"] timber pier legs rest on tapered concrete anchors with adjustable height, galvanized steel brackets clamping the timber firmly in place. The top of the pier above the obs floor is clad in 18mm plywood. I used thinner, 15mm ply cladding below the obs. floor.

The image shows a very early state of the pier legs standing inside the octagon framework before plywood cladding was fixed. The pier feet were pushed out to the inside edges of the octagon to provide a strong four sided, pyramidal form of maximum footprint. The builder's ladder shown here was soon replaced by a professional quality, warehouse stepladder with handrails. 

This stepladder has been a huge safety factor in my long term comfort and survival. The deep treads provide feedback to help me balance while constantly carrying stuff up and down. While I can rest my elbows on the handrails when I am carrying heavy loads with both hands. The hatch at the top of the ladder rises up to stop between the tops of the handrails. Allowing sliding, door bolts to quickly secure the hatch in the open position.

The pier's plywood sheeting was only extended downwards far enough to allow plenty of head clearance while standing on all four sides under the pier. This allowed free access to the outer area of the octagonal base of the building for timber storage. 

I literally climb the stepladder inside the pier to reach the observatory floor. Much as I did on the ladder shown.  I had to cut out a dog kennel shape to allow my head to rise unimpeded for the last few steps. Most days I climb up and down the stepladder at least a dozen times. There is always something to fetch. Usually tools. The obs. floor height is 2.64m above the concrete slabs laid on the ground floor.

13.10. Still, no clear sunshine. I have parked the telescope and am going in for lunch.

I spent the afternoon working on the mounting to find a better position for a longer turnbuckle. I wanted to re-use the existing, stainless steel U-bolts but they were fitted to the bearing housings. With the nuts deep inside. Which required a lot of work to remove several bearing housing plates to reach them.