Author: IMT

24th March 2021

With some wet weather coming in I decided to put a tarpaulin over observatory walls as we had not fitted the dome yet. I used an old pole from a bird feeder not currently in use and the pot used for checking the concrete mix with the slump test.

I then fitted the electric cable that would be connected to the outside socket once the dwarf wall was built. I had forgot to run a rope or string through the plastic down pipe but still managed to get it through with a bit of pushing, including the run for the pier and the main outside wall.

22nd March 2021

Time to prepare the observatory walls to be fixed to the observatory concrete base. Because this observatory had been in place at my last house, we cut the mastic to separate the panels. This left large amounts of mastic on each of the dome segments and on the observatory wall panels. With the use of Stanley knives and an electric sander the job was much quicker than using sandpaper by hand. It still too several hours though.

Then it was a case of placing the wall segments down and biting each pair together running a bead of mastic down each. Now with 2 pairs done, we lined the dome up so that it was at best equidistant from the pier. I then drew a chalk line around the edge, drilled pilot holder where the dome walls would attach to the concrete and then we unbolted and moved the dome walls again.

Luke then had the fun of using the SRS drill which is the only drill to get through concrete to the depth needed for the long M8 bolts. Once all were drilled and the anchor bolt sheaths were hammered in, we ran another bead of mastic around the base and then placed the dom walls in their final positions. We then bolted them to the floor and the 2 pairs back to each other with more mastic here too.

By this time it was a getting fairly dark so we tightened up the final set of bolts and called it a night. Luke then spent some time raking the mounds of soil from around the sides and rear of the observatory that use to make up the vegetable patch. The lay of the land means we need to build up one end of the observatory land surrounding the dome by about 6 inches to allow for a flat patio later in the summer.

Finally the day after this I came out early in the morning and ran 2 tubes of silicon mastic around the outside of the observatory so that when I pain on the Rust-Oleum fibreglass Fillcoat waterproofing sealer that it would smoothly go over and not disappear in some of the larger gaps caused by less than professional concrete laying.

20th March 2021

Another weekend, another day of concreting. Once done, there are 3 patios to fit, another observatory, rolloff, a Summerhouse and a workshop! That’s a lot of concrete and cement mixing!!! So you guessed it, more ballast!

Similar time as before 8:41 am and Luke and I removed the carpet from the old concreting which separated the block from the observatory base. This was carpet and plastic. We worked out that removing it was hard so the next time we would remove after 4-8 hours, time for the concrete to set and not slump but not so hard you have to use a cold chisel and lump hammer to remove.

Given the depth of the South side of the observatory base, we decided to place a lot of flint material on the base, this again would reduce the need for so much concrete. Another slump test and another successful mix.

By 10:40, some 2 hours later we were done. The join was a bit rough but we could chisel that down later if needed.

The spare cement was used to concrete in a manhole cover that was not concerted in by my house, also I used some to start the base of the small brick pillar nicknames Fraggle Rock by Gingergeek and 2 bricks for the electric to be fixed onto later.

Just before evening set in I went to inspect the concrete and cover before it got cold, I noticed a bird had clearly walked across it, that will now be some heavy bird I guess 🙂

17th March 2021

During the week whilst waiting for the ballast to arrive for completing the observatory base, I took the opportunity to unpack the weather station, all sky camera (ASC) and Ring camera that would go on the aluminium pole in the garden.

I’d forgot how many wires there were for all of this given the ASC has a due heater built in, another set of wires and we had a secondary rain sensor connected. This was never commissioned at the IMT3 location so we removed from the setup and simplified the wiring, I must remember to give it back to Bob who kindly provided it.

The USB connection was in a waterproof box, this was for the ASC and the heater connections were here too. Gingergeek and I cleared out the spiders that had nested in there, filled the holes where they got in and did the same inside the ASC itself.

The Unihedron SQM was also unpacked and we have decided this would go on a separate post.

Meanwhile we unpacked the anemometer and repositioned it on the pole and allowed the ASC to positioned at the top to give an unobstructed view.

All set and ready for installation.

13th March 2021

So continuing my writeup of progress on the dome build. With the pier block complete, now it was time to make the former for the base and start the concreting. The former was made from 5mm ply that I purchased from Homebase as they cut large sheets on site which is very hand for transport. When home I then cut the material further and then secured the strips together with some scrap wood I found.

With some rebar stakes found in the flow borders I kept the wood former in place. Again I cut a hole in the wood seen to the right of the photo above for the electrical pipe. The height of the block above the ground can be clearly seen.

With the ability to meet 1 person outside, one of my friends came over to help. I had already prepared some days earlier the wood former which was looking good. I noticed that to get the depth required the height of the observatory base to the North was significantly less than to the South due to the slope of my land. So I needed more ballast.

Travis Perkins was the cheapest for ballast locally and had delivered before. The driveway is rather tight at the property, however the drive did his usual finesse and reversed up first time. He then set about manipulating the fantastically well engineered crane are to move the bag to the rear of the vehicle without hitting my lamppost 🙂 Well done Mr TP Driver.

In hindsight I should have made the overall depth much less including that of the pier. I could drive a car on the base or build a house it was so thick, This in part was because we decided not to dig any further into the chalk for the pier block and instead have the block higher to make sure it was still thick enough.

Again the level of the wood was checked across the former to the pier block to make sure the level was correct. By 8:40am we had poured our first load and the long process began.

It was clear after around 5 pours that this was going to take some time and a lot of ballast! After 2 hours it was obvious that we did not have enough ballast and the empty bag stopped us progressing any further. It would be another week before we would have another opportunity to complete the base.

Later that night I found some rebar in the garden and Luke and I hammered it into the concrete to give the next pour in a weeks time something to anchor too Carpet and plastic was used to separate the pier block from the observatory slab.

21st February 2021

It’s been slow going since January. Lots of cold weather, rain and broken ribs had stopped me in my tracks from concreting the pier block. However on 21st February I finally had warm enough weather and a lot of help from Luke to start pouring.

We placed some flint in the bottom of the hole to help reduce the amount of concrete needed and to push up against the chalk. We then started measuring the cement and ballast out. We used Bob’s notes from our last concreting party which was 6 x 10kg buckets of ballast to 2 x 6kg buckets of cement. The water we used a bucket with a marker pen line on and then heaved it into the cement mixer.

The first slump test was perfect. The first pour looked good too. 2 hours in and we were 2/3rds done and nearly up to the downpipes that is to be used for cabling.

Before we started I made sure the wood former was level all the way around. This makes it super easy when pouring concrete, so as long as you pour to the top of the former it will be level as we proved on the final pour.

We then took 3 pieces of rebar that were lying around the garden and placed them where the pier would go. We performed a test fit of the pier housing, some air-conditioning duck so make sure the pier was central to the block. I must at this point thank Ian Piper who’s idea it had been to put the concrete pier in. At a cost of around £50 for the material this would be far cheaper than the £1,000 pier I purchased in the past and the £500 not so great pier I purchased from Pulsar Observatories.

After just over 3.5 hours we had finished and that included the final brushing over the concrete to make it smooth. Thanks Ian for the pier suggestions, Bob for the mixer, Mark for the enthusiasm, Luke for the help, Nigel for the base design and of course Helen for putting up with me and my hobby. A good start, next stop was to concrete the dome base.

2nd December 2020

So now the work begins. How to turn a vegetable patch into an observatory. The first thing any good person does when moving into a house is perform a harvest! So we set about harvesting and found some rather large parsnips (which we have been having every Sunday lunchtime since) 🙂

Once done, we removed the edging boards and marked out the dome diameter using the stakes we found in the garden.

Once done I left Luke to dig the rest of the dome base out with a little help from my daughter and as you can see digging in a vegetable patch is rather easier to start with than hard ground due to years of using the land.

Okay, so that’s the dome base which is a nice 6″ deep. Next, which was a slightly bit more problematic was to dig out the pier base through chalk to a depth of 65cm x 1m wide. Yes I know I am mixing my scales but that is because I can 🙂

I then had to wait several weeks for the weather to improve before I could start creating the former for the hole.

I must add at this point, that despite building and installing many domes before, I sought out the experience as one should, of another astronomer and friend, Nigel, who sent me a well prepared document of contracting a concrete base, that I have used as extra guidance on this dome build.

Next up will be more preparation for the foundations and connecting the electric and ethernet from the house some 100m away the way I have to run the cables!

21st November 2020

So after the shortest time in a house, I have now moved to a much better astronomy home, surrounded by fields and forests, ancient woodland and with some of the darkest skies in the North Hampshire Downs. I am fortunate in my location, however less fortunate that the build of this observatory, unlike my other observatories is happening in the middle of a pandemic of Covid-19. This as you will see makes it extremely hard when you can’t have astronomer friends over to help with the preparation and installation.

The move started to with the dismantling of IMT3 and in the final days at the previous house we dismantled the dome, at least at the time I could have some friends over to the garden to help with Mil Dave, Alan and Shane lending a much needed hand.

So on a quick dismantling, which was much quicker than constructing the astronomers put the dome segments on the lawn 🙂

However as I found that night when a storm front came through, which caused me and my daughters boyfriend to get up after midnight to secure the dome segments in a more wind resistance piece of the premises.

The following day Luke has had his first angle grinding lesson to take out the remains of the bolts and plugs which to be honest I think he really enjoyed.

Then the moving day came and I put all the important scientific astronomy equipment in my old Landy to make sure it got there safely.

whilst the rest of the observatory went in a further truck kindly supplied for free by our removal company who are the best removal company ever! Thanks Camberley Removals!

By mid November, some 4 months after we accepted an offer on the house I landed up with my new more astro friendly observing location surrounded by fields.

Next up is removal of the local vegetation and preparing the ground for concreting.