Dome build: First rain test and equipment musings.

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Tuesday: Went out to check the dome paint's waterproofing qualities after a night of rain. I am delighted to report only two small dark patches high up. I'll record their position and check the area outside when it stops raining. Given the small quantity of leakage a second coat of paint might just seal it. The other dark stains are previous leaks when the dome was unsealed and unpainted.

I needed a torch to see anything in the dome. It really is very dark in there. The rain continues. So I will monitor for further leakage as the day goes on. At least it wasn't dripping anywhere. The rubber skirt is doing its job with no sign of leakage onto the top octagon ring. Though I do need to make some water bars for the bottoms of the veranda doors. The strong wind had blown rain in under them.

It may seem odd to some of my readers but I really haven't given much thought to using the observatory. The mounting has been safely covered for months as I beavered away providing its shelter. I have watched the Sun, Moon and planets crossing the sky without being able to point a telescope at them.

First I have to rebuild and fit the 7" f/12 refractor onto the big mounting to check its clearance from the dome. That will set how long a dewshield I can fit without a collision with the woodwork.

I'd like the 6" H-a refractor fixed alongside the 7" for viewing the solar prominences. That means balancing the extra weight of two instruments. I'm still not sure how many 5kg 9" Ø weights I can fix on the Declination shaft. There is a brass spacer I fitted to push the weights out as far as possible. With only the three locking screw collar clinging to the end of the shaft.

The 6" needs only a single weight. So I might just get away with three counterweights or 15kg for the pair of telescopes together. It depends whether the Dec worm housing is going to prove a nuisance. It could be rotated by 90° but then, it may not clear the wormwheel rim.

Which reminds me that I should paint the weights white to help avoid collisions with my head in dim light. I might just have to get a longer length of 50mm stainless steel shaft to make room for more counterweights. Fortunately it is very easy to swap shafts thanks to the Tollok clamping bushes. Apart from handling the sheer weight of the shaft itself, of course. They really are "lumpy!"

It may seem like excessive fuss over a few counterweights but I'm thinking of the future. As old age takes its toll my ability to lift heavy weights to the height of the mounting is bound to reduce. Lifting a weight above head height requires a stepladder. Moreover, I never fitted shaft locks or brakes to the mounting. The clutches on the wormwheels are protective. Not intended to lock the shafts against severe imbalances. Loose weights on a bare shaft waiting, for the locking ring, could easily cause it to tip downwards with catastrophic results. The damage to the floor and ladder from 15kg steel disks falling from such a height would not be light. This assumes they miss me as I teeter high on the ladder.

I tried using a slot in the end of a length of timber to support the shaft while I loaded the counterweights. Though this is not completely safe unless the timber prop is securely located and the bottom resting on a firm surface.

Click on any image for an enlargement.

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