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cloudnine

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About cloudnine

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    Ottery St. Mary, Devon

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  1. Sad news indeed. I have 1962-2016. What will my family buy me for Christmas this year?
  2. I'm a bit late to the party, but my pulsar dome was installed just over one month ago on a DIY concrete base. I love it! It has transformed my observing as (a) I am naturally lazy, (b) the equipment is set-up and ready to go, and (c) being shielded from the breeze make for more comfortable and hence longer observing sessions! Based on the evidence of reading the temperature inside the dome at the start and end of observing sessions, where the temperature drop over the course of a couple of hours is only about 1 degree C, I reckon that the dome is thin enough and the concrete shield
  3. Final post, containing a pictorial evolution of the whole thing from start to finish... buckle up. Am happy to take any questions now or sometime in the far distant future.
  4. You won't regret using a mixer. I poured an approximately 60 x 60 x 60 cm cube a couple of weeks ago and the mixing took about an hour. I'm no expert, but curing can start as little as one hour after mixing depending upon conditions. I used mastercrete... the tech spec states that it reaches 25% final strength after one day, and something like 75% (from memory) after seven days. I would be wary about drilling and inserting expansion-style bolts too soon as I'd imagine the localised forces may be too much if it hasn't reached a reasonable strength. I'm sure others might have a better
  5. I haven't revealed what is going in there The scope that is initially going in the observatory is the type of scope you wouldn't put in an observatory. A 12" dobs-onion. Makes the central block pointless, as well as not being able to get near any horizon. However, sheltered observing is much better than exposed observing. The longer term plan is to install a 12" SCT-style scope on a monster mount and pier, but that will take at least a couple of years of savings to achieve, unless I win the lottery.
  6. What's a few inches between friends. I went for octagonal because I thought it was better to mix less concrete (i.e. saving having to mix corners). It made my shuttering a lot more challenging. Good luck!
  7. Looking good. I wasted a good year thinking about making a dome, and then making a roll-off-roof obsy, before deciding to buy one instead (primarily due to time-constraints and too much procrastination). Hats off to you for getting the project off the ground. Look forward to seeing how this progresses! Martin
  8. Pad minus 7 days 16th July 2016 : pouring the foundations and central block This is the first big day of concrete mixing. Everything I've read and watched becomes academic. Mixing consistently and quickly is key. Given that all the ballast is in 25 kg bags, just the thought of continuously shoveling from ground level made my back ache. So decided to make a platform out of an old composite worktop upon which to lift the 25 kg bags, and then slit open the bottom of the bag to produce a pile of ballast a couple of foot off the floor. This turned out to be my saving grace. Shoveling ball
  9. Pad minus 4 days 19th-20th July 2016 – Gridwork! The concrete pad will be supported around the edge by the strip foundations. Why strip foundations? Firstly the garden is on a slope, and secondly a lot of landscaping had been performed by previous owners meaning that the top layer of soil wasn't natural. Having strip foundations is a lot more effort, a lot more soil to shift, but is necessary to provide a stable base given the weight of the concrete pad. Wouldn't want the eventual observatory to relign itself inexorably downslope! Despite the surface layers feeling quite firm to
  10. Thanks The two wood strips provide four benefits. Firstly, they held the central block in the right position inside the octagonal frame. Secondly, when pouring the slab they proved useful for separating (at least on the surface) the four sections into easier-to-manage float-finishing jobs... There is no way I could have floated the entire pad in one go given how long it took me to mix the concrete. Thirdly, water-ingress is a common (apparently) issue with observatories, so chasing out the wood will provide drainage channels for the inevitable 'flood'. And finally, yes
  11. Pad minus 1 day (yup, I'm going back into the past with this thread ) 22nd July 2016 – final preparations Like most things you haven't tried before, the time it takes to prepare is always a surprise. Today I thought that I could finish off some formwork in the morning and pour the pad in the afternoon. As mentioned in tomorrows entry, the pour was delayed due to a 10% chance of heavy-sustained downpours mid-late afternoon (slow moving air masses with unstable upper layers). Of course 9:1 chance of no rain, which is exactly what happened, but the risk wasn't worth takin
  12. Thanks :-) Concreting is hard work, and something I would have much preferred paying someone else to do, but the nature of the job put people off, as did the requirement to transport the 110+ ballast and cement 25kg bags from the front of the house, through the garage, and down a steep run of steps. The latter took me over four hours alone... Sensibly I had it all delivered one week prior to the first pour (foundations and cube) to give me a week to recover!
  13. I should be ashamed for not crediting my lovely wife for helping with the tamping down!
  14. Today is the 24th July 2016. Yesterday the long saga of the observatory base ended. I ache, but am not immobile, I slept long and my head is slightly fragile but not enough to take ibuprofen. I start this thread to document how I got to this point in the hope that others might take heed of the difficulties, uncertainties and the rewards of building your own concrete base. 23rd July 2016 - the final pour Today will be the culmination of months of planning. The weather is forecast to be cloudy with sunny intervals without the risk of heavy sustained downpours that delayed the co
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