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10.37[CET] First image today of AR2882 approaching the eastern limb. Rather modest transparency. 3/5? Some thermal agitation. 3/5? Poor imaging results. 3/5.
Beginning the usual focusing and etalon tuning rigmarole in search of improved images.
11.00 Small clouds crossing rapidly from the WNW. The blue sky is white in the east. Image quality reducing. Back to working on the dome!
I took a photo looking down on the bottoms of the closed shutters. Then measured and drew the same with dimensions. I had stretched a cord tightly around the outer edge of the slit ribs for a reference line.
The narrow space available for the shutter boards and drawer slides is obvious. Also how thin and asymmetric the shutter boards will be. These are vital components. Since they carry at least half of the considerable weight of the shutters.
The drawer slide supports may need to be extended upwards to provide some extra "meat." This will leave room for bolting the slide supports to the shutters. These boards are shown in yellow.
Later I used the 360° laser to measure the squareness of the slit/shutter ribs in comparison with the zenith board. Measuring from the line projected on the ground, while the same line was simultaneously grazing the edge of the zenith board, proved a 2cm difference to the slit ribs.
I am not sure how important this is. Or even if the laser line is accurate when projected overhead. I set the laser body on the base ring to minimize the projection height. The laser cannot project directly overhead. In fact there is a small protective cover over the top of the laser diode.
This has been a priceless tool during this dome build project. Its internal pendulum assures the projected beam is level in all directions. The additional vertical beam is a great asset for ensuring perpendicularity and straightness of ribs and other components.
The prices of these tools seem to be falling steadily. Now costing about the same as many, popular, portable, power tools. I chose the Bosch Universal Level Solo 360 and have never regretted it. It uses four, ordinary AA batteries. Which seem to last for years.
Here it is shown in the plywood dome checking the dome's, base ring level. As mentioned at the time: It managed this task instantly. Rather than the countless man hours I have utterly wasted using builder's levels and straight edges over the last couple of years. Or even a home made water [hose] level. Which nearly drove me to distraction!
The Bosch has a tripod bush and [very] cleverly locks its internal pendulum automatically when switched off. Its laser light flashes if its base support is not reasonably level. Though it seems quite tolerant in this respect. No extra effort being required beyond quite ordinary, common sense. I usually place it on a stack of timber off-cuts or plywood to adjust the height. Most importantly, it doesn't care if the surface, onto which it projects, is flat or spherical.
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