21.12.2020 Keep that dome rolling.

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Monday 21st. Another grey day in prospect. No sign of Jupiter and Saturn close together yesterday evening. You wait 800 years and then cloud comes along. It's just like the total solar eclipse expeditions of the past. They'd sail off in hope of capturing vital information. Then it would be cloudy at their carefully calculated site on the other side of the world after months of travelling and preparation.

I am expecting the 360° laser level in the post. So I can try that on the old dome. I have never been able to confirm the individual heights, or levels, of the 180mm [7"]dome rollers. Hopefully I shall finally be able to do so now. It will be good practice for the new dome ring. 

I should have taken this image with the slit open for more light but it wasn't possible because of the weather.

As soon as it arrived I quickly unboxed the laser level. Then fixed it on my old video tripod with rise and fall, pan and tilt head. Set it up on the observatory floor and quickly levelled it. Switched on and enjoyed instant confirmation of the dome's base ring level. The green line was astonishingly bright, sharp and remarkably useful. 

When there is a change in level of the dome base ring, on the rollers, it tries to climb uphill. Which momentarily increases the resistance to turning. There does seem to be a small difference in level of the tops of the eight rollers. One particular roller is 1/4" high. Now I should really rotate the dome to detect if there are any changes in level of the dome base ring. 

I wish I'd had this amazing tool when I was building the original observatory. Though this model of the Bosch 360° level has only been released this year. They used to have red lines but the green is clearly superior. The human eye is most sensitive to green. Red is not.  I have struggled with a red laser range finder in seeing if the distant spot is on the target surface.The new level is self-levelling via an internal pendulum. I measured the laser line as only 1mm wide at 5' from the level. Ideal.

On the trolley front I have made a proper 2.2m radius bar. This is to confirm clearance of the nested segments from the jockey wheel jacks. It would be a bit silly if I couldn't fit them on the trolley when they arrived.

I set up a few tall items around the newly marked 4.4m circle and was shocked how large it seemed. It was worse when I stood a length of timber on end at the centre to represent the height. I can see the pole at eye level when seated at my computer in my upstairs window. This thing is going to be colossal! It is going on top of the [expanded] building! Eek! 

I ought to get some 3/4" plywood to make curvature templates for the building and the foundation blocks. With the worsening virus toll some shops are going to be closed until after the new year at the very least. I have no idea if that applies to the builder's merchants.

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