24.12.2020 360° Laser level checking the dome base ring.

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Thursday 24th A mixed day of mostly overcast and occasional rain. 

I opened up the dome to have more light for some images of the laser level in action. It promptly rained as soon as I went indoors to download the pictures!

The first image shows the Bosch 360° laser level on my old Bogen video tripod. I bought the Bogen secondhand over thirty years ago. The paper scales have lifted over the years but the tripod still works as new. It is heavy but sturdy.

The laser level has an internal pendulum so is self-levelling over a limited range of base tilt. The pendulum is cleverly locked when the power switch is set to off. Making the device rather more robust than some examples. A Mode button, on top, turns the vertical, laser line on and off.

The bright green line travels right around the dome except for where the big mounting casts its shadow. This just needs the tripod to be moved to one side to throw a line onto the missing bit. This tool is absolutely invaluable if  you are building a dome from scratch. Or setting an existing dome up on its rollers. Normal people use them for laying bricks, putting up wallpaper or setting tiles.

You would not believe the hours I have wasted trying to establish the flatness and level of my own, dome roller ring. The 360° laser level gives instant confirmation. Leaving nothing to guesswork. 

The second image shows the green line projected on the edge of the base ring. Even in daylight the line is very bright, sharp and clear. Tests indoors, over much longer distances, 15+m, showed that the line expanded to 2mm. Still easily usable because it remained that width over the entire length of the far wall.

I have tried 3m long, straight edges, builder's levels and water [hose] levels and I was always unsure of my results. Straight edges are never truly straight. Builder's levels only rarely, perfectly accurate. Water levels have a near invisible meniscus [in clear hosing]  to confuse matters. The sheer weight of the water-filled hose was always a serious problem.

I would have to support that weight with prussic loops of cord and hanging screws. I spent more time refilling the hose with water, using a small funnel and a jug, than checking levels with it. The slightest change in level of one end and the water would fountain out of the lower end!

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