Thursday: As if through a cloth darkly.

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The need to darken the observatory interior has been hovering on the back burner since it was built. The rather pale and naked, birch desktop merely gave me a shove in the right direction.

I wanted a low toxicity finish given the hours I often spend in there even when it is hot. The finish had to ignore the occasional leaks and the existing black stains on the dome's birch plywood. I had no desire to use a toxic fungicide on this either. What to do? Put it off for another month.

Then I thought of black, garden fleece. A non-woven fabric used for suppressing weeds. I wanted a dark colour but black was not available locally. So it was off to the city to a chain of outlets which [unusually] has no online sales system. The traffic was awful with a couple of hours completely wasted in traffic queues at well over 80F watching receding, but unmoving brake lights through the windows of vehicles in front.

The fleece material comes in two options. One at 50g/m^2 and the other at twice the weight. The thicker stuff was in narrower strips than the lighter. So I bought enough of both. The dome gores will be cut from the heavier cloth running vertically. The walls cut from the lighter  but running horizontally. I didn't want any unsupported seams.

My wife has been using this stuff in the garden for years and can confirm the quality of this particular source of material. She has even used it as windbreaks and it has lasted well. Much of the competition is reported as flimsy and literally falls to pieces in no time at all. I should get a few years wear out of this better stuff.

The dark material will be stapled to the dome's wooden framework. Leaving an air gap from the dome's outer skin. Being able to breathe freely it should avoid dampness. It might also block some solar heat gain coming through the plywood skin. Best, is that it will hide the ugly stains from view. Oh, and make the dome darker inside.

A little practice on scraps showed that stapling to birch ply is hard work. No penetration! So I will have to staple the cloth only to the framework rather than the ribs. Then I just have work out a neat way to tidy up all the edges to my satisfaction. Yet again the flat, trapezoid panels reward me in my not having to manage a sphere.

Now I just have to drag a set of stepladders upstairs to be able to safely reach the dome's zenith. Two done by lunchtime. About half an hour for the second. Any creases can be undone by removing staples locally and easing. I chose to cover only the bottom three panels in each drop. Since the upper panels do not share the same frame.

Six drops in total by 16.30 when I had finished one bag of fleece. Getting into a routine now but a bit slapdash on the final edge trimming. The cloth appears very dark indeed when up-lit only by the open stairwell and open front door in bright sunshine below. It will be even darker when the entire interior is covered in fleece. I think the finished result is acceptable rather than great. It would have been so much easier to slap a load of matt paint on the inside of the dome to hide the worst woodworking atrocities.

Friday: Woke with an aching back from yesterday's paper fleece hanging exercise. Perhaps I'm still recovering from the gravel shovelling? Plodding on with the "blackout curtains." More done, 5 to go. Cut the pieces of cloth to length and width in advance to save running up and down. Tried a fire test of the polyester[?] cloth with a match. It is slow to catch fire but then burns like plastic. Dropping melting "fire drops" onto the floor. Nice!

Pm: Plodded on again until I had used up the second bag of fleece. Now only one full gore and two "halves" to go. The drop in scattered sunlight is quite useful for solar but difficult to capture with the camera. Matt black paint would have been darker. The effect is certainly cumulative as each new surface no longer allows reflection. A slight worry is off-gassing from the cloth. It is not sold for interior use. Though the dome is as [air] leaky as I could manage. Various forum members have set my mind at rest on its use.

I have just been watching a small bird from the window. It was climbing all over the observatory and veranda in search of insects or perhaps spiders. It was so agile, as it walked effortlessly up and down the plywood walls, that I imagined it to be a Treecreeper. The binoculars soon helped to identify it correctly as a female or juvenile Greenfinch.

Click on any image for an enlargement.

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