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It is now a year since I wrote Page 5 of this account, and there has not been any further ingress of water into the dome. I have always been willing to agree that the original ingress may have been due to an unfortunate combination of circumstances (heavy rain, high winds, and the dome in an unfortunate position). I cannot say if those circumstances have occurred again in the last year. I did implement the manufacturer's recommended solution to the original problem in such a way that the gap is, as near as I can determine, sealed by the two strips of rubber. These have stayed in place; the closing chord seems to have cut through the upper strip but has done so cleanly so that the strip is intact right up to both sides of the chord. (I say 'seems' because I cannot see it and I have judged it by feel.) I have become aware that what I described as the second leak (Part 5) may have a different cause. I certainly get condensation on the inside of the dome and this runs down to collect on the shelf, below which are the supporting wheels (see diagram in Page 5). For some reason this condensation seems to be worse in the section 180° away from the opening, which is just where the "leak" occurred. Thinking about it now I still think the water was most likely rain water coming in under the dome, but I cannot rule out the possibility that it was condensation forming on the inside of the dome. I have certainly had such condensation to the degree that it dripped onto the floor. However in the original observation, it all occurred during one wet night, and I think it less likely that that much condensation formed during one night. I have a remote-reading hygrometer in the observatory and, when it leaked (both times) I knew something was wrong because the humidity went to 100%, which it has not done before or since. This is despite having to mop up condensation from time to time during the winter. The only solutions to the condensation, that I can see, is (i) to spray in inside of the dome with an expanding foam, or (ii) to increase the ventillation. The former is not really very practicable but would have the advantage of increasing the opacity of the dome (red light certainly penetrates it so I assume infra-red does too). I originally asked the builders to provide lots of controllable ventillation, but they realised when the dome went in that planty of air came in through it that further ventillation was not necessary. Of course I have blocked up the primary source of that ventillation. I have tried a small dehumidifier, but that has proved useless partly because it is too small, but mainly becaise it simply ices itself up in the cold weather. ConclusionSince implementing the manufacturer's solution to the original leak, and the adjustment of the rubber seals for the second leak, I have had no more occassions when rain has penetrated the dome. I do get condensation on the inside of the dome, which concerns me, but I can see no obvious remedy. |
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