From Micro Obsy to Dual Pier Observatory - via Hard Work, RSI, Back Ache & Melting Credit Card!

[ArmyAirForce]

The new mixer made short work of mixing the concrete for the foundation at the bottom of the hole. This was just a thin layer to form a flat base for the next step. Three layers of high density concrete blocks will be built up in a square with a hole down the centre. Blocks are much cheaper per kilogram than concrete to mix.

The centre of this square will be filled with more concrete, in addition to the space between the outside of the blocks and the hole in the earth. Four re-bars are fitted up the centre of the square and a further four will extend up to the top of the pier tube.

[ArmyAirForce]

I could do with having the frame assembled outside when I pour the foundation for the pier. The top of the foundation height is related to the floor height, which in turn sets the pier height. So I decided I needed the joists and legs waterproofing. So this morning, I spent 3 hours painting the original corner legs and the new intermediate legs, then turned my attention to the main joists. All the intermediate joists will need painting too, plus the underside of the shed floor, but I can't do any of that until the piers are in.

After a quick lunch, I set to work digging the second pier foundation hole. All I can say is that I'm pleased I didnt dig this one first; otherwise, my observatory may have only had one pier!! It was very hard going, with lots of smaller one to two inch stones or bits of brick in the upper layers. This meant my spade couldn't dig through it and I had to resort to a small gardening trowel, which due to its more pointed end, could cut between and push passed all these small stones. As I dug further, I started to find larger bricks and what I thought was a complete brick at first, turned out to be a five to six inch slab of very hard concrete, wedged under and over more bricks.

I had to mine under and around it before belting it with a small sledge hammer, breaking it up into four main chunks which still put up a fight to remove! The further I went down, the more large stones and bricks I found. My dodgy elbow was killing me.

Edited May 10, 2022 by ArmyAirForce

[ArmyAirForce]

By the time the school pick up run was due, the hole was almost at full depth, but it fought me all the way. Five full wheel barrows of heavy clay soil came out of the hole, along with this pile of bricks, concrete and stone. You can see a brick on top of the pile to give scale to the lumps! I could barely lift the trowel by the end of the day.

Below is the second hole, almost complete. My placing of the hole, dictated by the nearby tree stump, was fortunate. As I dug down, one edge of my hole fell exactly in line with one of the brick walls from the old air raid shelter ( inset ). These bricks are very hard and the wall is double brick thickness. I had to smash one wall out when the conifer hedge was cut down along side the garage concrete hardstand. This was so the tree felling team didn't damage their stump removal machine on the bricks. It was a nightmare to smash the bricks out and I broke one hammer and damaged another getting them out! So I'm really fortunate the edge of my hole was flush with this brickwork.

[ArmyAirForce]

I got the other side of the legs and joists painted this morning, then went out to carry on digging. I got to the bottom of the second hole at seven wheelbarrow loads, plus the huge pile of rocks. I just got some hardcore into the bottom of the hole when the rain came. It's stopped now, but I'm not keen on kneeling/lying on wet ground, trying to smooth out concrete at the bottom of a two and a half feet deep hole. My daughter will be home from school soon anyway, so I've got my feet up and coffee in hand!

I'll have to photograph the huge spoil heap that the observatory has created! ( EDIT - picture added ). This will go into leveling the land beyond the observatory where we plan a second lawn and a 1/1 scale railway garden feature!

The spoil heap is 23 feet long, 2 to 3 feet high and about 5 feet wide!

Edited May 11, 2022 by ArmyAirForce
picture added

[ArmyAirForce]

The ground was moderately dry after 6pm, so I went back out and mixed up the concrete for the base of pier 2 and left it covered with some plywood in case of further rain. However it is meant to be dry and clear all night.

After I cleaned up and put the tools away, I did a minute of astronomy with my phone, with the two piers in the foreground and the 77% illuminated, 11 day old Moon at 35 degrees altitude in the South East.

[ArmyAirForce]

This morning, I went out to work on the piers. The concrete foundation for the first had been dry a few days, so I started laying the blockwork. It was hard work laying the blocks so deep in the hole and I had to climb into the hole for the first layer, being careful not to stab myself on the rebars. Layer two was easier, but still quite a reach to lower the blocks in place without following them into the hole!

It took about 90 minutes to get the first twelve blocks in place. The first 180Kg of the foundation.

[ArmyAirForce]

Even though I laid the second pier foundation yesterday evening, it was firm by late morning today. I hadn't expected it to have cured, but it gave me the opportunity to get the blockwork in for the second pier. Another 90 minutes passed and the second one was done.

The blockwork needs to fully dry before I can pour the concrete inside and out, but I also need to wait for some more rebar coming in the post. Local stores were all out of stock, so I had to go online. The new rebars will be set into the top of the foundation block, then extend up into the pier. The existing bars will extend six to eight inches into the bottom of the pier. The foundation concrete will need to set enough to support the upper rebars and also be firm enough to support the weight of the concrete when the pier is poured.

This view of the two foundations is looking approximately South. The way the piers are staggered gives them both a good view South and gives me my small warm room space in the left foreground. The right pier will be for solar system targets while the left will be for deep sky.

[ArmyAirForce]

This morning, the eight extra rebars I ordered, turned up in the post. I wasn't expecting them until Monday. Unlike the bars from B&Q which were varnished, these weren't and were covered in light surface rust. I didn't want to stick them in my concrete going rusty, so cleaned them all up with a rotary wire brush in the pillar drill and then painted them in hammerite.

Since I'm almost in a position to pour the piers, I made these wooden supports to hold the rebars straight in the hole while the concrete is poured. The lower cross holds the bars in the base of the pier while the second cross supports the bottom of the rebars that extend up into the pier.

The cross also fits the top of the pier tube, so when I come to pour that, I can also keep the bars straight. I only need one cross in the top of the tube as there's only four bars that extend up the tube.

[ArmyAirForce]

Today, the floor joists were carried out once again to check on the height between floor level and the top of the pier foundations. I needed about 12 inches. The deepsky pier was pretty much spot on with about 10 inches to the top of the joist, plus another 2 inches of the shed floor.

The solar system pier was a bit low by around a couple of inches. The easiest way to solve this was to add a layer of block paving bricks. So off to B&Q for eight bricks and a bag of sand and then back home to get them laid. This would allow the foundation concrete to be filled flush with the top, so the pier tube would start at the correct height.

[ArmyAirForce]

It didn't take long to lay the bricks, after which, the joists were all screwed together. As before, this is just a temporary measure for checking stuff. I'll probably be evening out the earth height around the piers once they are poured, so the weed membrane has a nice even surface to lay over. I'll want the joists out of the way again for the concrete pouring and digging.

My daughter gave me a hand out with one of the observatory end panels to check the pier heights against the rolling roof height. The piers were standing about an inch high, due to sitting on planks over the foundation holes. The pier adapters and mounts add another 22 inches on top of the pier.

[ArmyAirForce]

Allowing for the height of the pier adapter and mount, it should bring the telescopes into the roof cavity space. This means that if I turn either of them to the North West ( left in this picture ), they should be looking up the slope of the roof runner line as their lowest viewing position. There's little point in having the observatory wall any lower on this side, as there's a small woodland on the other side of the garden that would obstruct the view. If there's something really interesting going to happen in the North West, I'll take a mount off the pier and set a tripod up on the lawn, higher up the garden.

The weather forecast is for rain and thunderstorms for the next two days, so I'm unlikely to get the concrete foundations or piers poured just yet. I want to pour the piers as soon as possible after the foundation will support them, so the concrete gets a good chemical bond in addition to having the rebars providing support.

[AstroNebulee]

It's looking great so far, I'm really enjoying watching your build 👌, lots of fascinating detail, good luck with the rest of your build 👍

Cheers 

Lee 

[JeremyS]

Proper job 👍🏻👍🏻👍🏻

[Domain105]

That is looking absolutely awesome. Great job!!

[carastro]

Loving this thread, especially the title of it. 
 

carole

[ArmyAirForce]

After the heavy rain of yesterday, today was a hot day - probably too hot for hard work! I started off back filling the outside of the blockwork with concrete. Due to the amount needed, I'm not going to back fill the whole height with concrete. I've filled it to half way up the second layer of blockwork and that took 80Kg of concrete! The rest will be back filled with a slury of the soil and clay we dug out, possibly with a little cement mixed in. Knowing how hard the clay was to dig out, it will set hard and the block isn't going anywhere. Another 170Kg was poured inside the blockwork, to bring it up to the top of the bricks. This now brings the foundation total weight to 430Kg!!

EDIT - Actually, there was another bag and a half put in the bottom of the hole to set the blockwork on, so there's another 30Kg, bring the total to 460Kg.

I realised I was going to be short on concrete and nipped out for another twelve bags after the first pier was done. I should have enough now to do the second foundation and both piers. After getting back, I mixed up another three and a half bags to back fill around the outside of the second pier foundation. I couldn't pour it without more wooden crosses to support the rebars, so have left that until tomorrow when I can reuse the first set. Hopefully I can get that and the first pier poured. It was hot work and even with the mixer doing the hard work, I was melting by the end of packing away.

Edited May 17, 2022 by ArmyAirForce

[ArmyAirForce]

May 18th 2022 - This morning, we had some family visiting late morning. I figured there was probably enough time to sort the first pier before they got there, so made a quick start to the day, getting all the tools out. The wooden crosses were jiggled up the rebars until they came off the top, leaving the foundation ready for the card pier tube.

The cardboard tube was held vertically by another wooden cross over the top, onto which I'd tied guy-lines, which were staked into the ground. To minimise any concrete and water leaking from the bottom of the tube, I mixed up some of the clay soil into a paste, which was used to make a small fillet around the bottom of the cardboard tube and seal the joint between it and the foundation.

[ArmyAirForce]

The clay was left to dry a little while while I gathered up some bags of concrete and other items I needed close to hand by the pier. The mixer was started and I watched as the pile of concrete bags rapidly got smaller! Despite trying to use concrete volume calculators and work out the volumes of the foundation and piers, the bags just don't go as far as you think they should! Eventually I got to the top, the cardboard hadn't collapsed and all was looking good. The family arrived just as I was washing the tools down.

The top of the pier was smoothed out as best I could with a little pointing trowel, sliding it under the wooden cross that was supporting the pier. A long, double coffee and lunch break followed, before the family left and I got back to work.

[ArmyAirForce]

So after lunch, it was time to do the foundation for the second pier. Quite exhausted by this time, with an aching back, I could see why so many astronomers have a single pier and swap equipment!! The second foundation swallowed up copious quantities of concrete again and when it was almost full, I added the four upper rebars and used some bricks and a spare roof tile to hold them centrally in the hole and upright.

The last picture for the day is another looking South, with the solar system pier standing tall and the deepsky pier in skeleton form. It's nice to see the observatory finally rising out of the ground after all the digging out and filling in! The second pier will be poured tomorrow.

 

[AstroNebulee]

35 minutes ago, ArmyAirForce said:

So after lunch, it was time to do the foundation for the second pier. Quite exhausted by this time, with an aching back, I could see why so many astronomers have a single pier and swap equipment!! The second foundation swallowed up copious quantities of concrete again and when it was almost full, I added the four upper rebars and used some bricks and a spare roof tile to hold them centrally in the hole and upright.

The last picture for the day is another looking South, with the solar system pier standing tall and the deepsky pier in skeleton form. It's nice to see the observatory finally rising out of the ground after all the digging out and filling in! The second pier will be poured tomorrow.

 

Loving reading your build, well described and a joy to watch develop 👍

[ArmyAirForce]

May 19th - Back out again this morning to do the second pier. The lower wooden rebar support needed to be cut off, as the angle of the foundation bars prevented it from sliding upwards. Once removed, I filled the bottom edge of the tube with clay again to seal the gap. That was left to harden a little while while I wheelbarrowed several more bags of concrete from the workshop to the observatory site. By the time I got the mixer out, the power cable and a few tools the clay was dry enough to start pouring concrete. Like the previous pier, I used guy lines to hold the tube still and in place.

By the time the pier was done, it was time for lunch! I just had a short break and went back out. The mixer was back in use, but this time for clay and soil. I started digging out the clay from the spoil heap and making a very wet slurry mix.

Edited May 19, 2022 by ArmyAirForce

[ArmyAirForce]

Back filling around the top of the foundation with just soil shovelled in, wasn't going to be particularly solid due to too many small air gaps. The clay slurry was trowelled in and tamped down like concrete. Once set, it should be pretty firm; as it was when I tried to dig it out in the first place. I started on the solar system pier, the one poured yesterday.

It took several barrows of clay to back fill around the pier and bring the earth level up to the level of the pier foundation. This will give a smooth level surface for the weed membrane to stretch over, without any sharp concrete edges to cut through it. I need to give it a little while to dry and then build up the front edge further where the earth currently slopes steeply to the lawn.

[ArmyAirForce]

There was still plenty of time before my daughter got out of school, so I carried on mixing clay and filled around the second pier foundation. With both piers poured now, I need to pull up the existing weed mambrane, which doesn't fully cover the area and do some levelling of the ground.

When the ground under and behind the observatory is moderately level, I can spread out the new weed membrane and bolt down the legs for good. The perimeter joists can then be fitted permanently and I can start cutting the extra smaller joists to support the whole of the floor space. For now, this is where I'm at. Piers and foundations done, with a rubble sack over the dry pier and a roof tile over the top of the pier poured today. We had a little overnight rain, so I don't want them getting wetter than they need to be.

[ArmyAirForce]

With an aching back this morning, I decided today needed to be a slow day. The two tree stumps within the observatory perimeter were cut down closer to the ground. The wood was a little damp and combined with a chainsaw blade that has seen better days, meant it was slow going. Another stump to the side of the observatory was also cut down to the ground. I barrowed some more earth to the observatory and did some more levelling around the pier foundations and other areas.

At the front, I dug out the plants along the front left and chamfered the earth down towards the lawn. The area under the floor will be a void, with just the weed membrane covering the earth. I plan to box in the legs along the lawn and up each side, to fill in the opening under the floor level. Both piers are covered now and need plenty of time to harden before I think about drilling them for the mount adapters.

The next step I think will be drilling the foundations for the leg mounting bolts and once they are done, I think I can get the weed membrane down. Over the weekend, we plan to empty the garden shed and move it forwards and towards the observatory to the new concrete, allowing space next to the garage for my trailer. That will also give access to an outdoor power socket which may be tapped into to supply mains power to the observatory. I need an armoured cable for that, which will run up the bottom of one of the roof runner supports.

Edited May 20, 2022 by ArmyAirForce
spelling

[ArmyAirForce]

A big update today!

May 21st 2022 - It's been a long hot day, but I feel I've made some real progress on the observatory - progress that isn't just digging holes and filling them back in again! The first job was to drill the concretefootings to mount the metal plates for the remaining six legs.

With those done, the first weed membrane was spread out on the lawn so I could measure out where to put the holes for the telescope piers. The two pier locations were carefully measured and drawn onto the membrane, before cutting the holes into multiple petals with a scalpel.