Author: IMT

10th April

A lot of progress since my last blog. I have gone from an empty shell of a dome to an observatory able to take a first light photo!

The first challenge was the dome rotation. It was binding. I quickly found out, with the help and advice of Dave Boddington, that in fact the dome was not circular and in fact it was oval in one axis by around 2cm. This was enough to pull the walls in causing the dome to bind. So a quick look around and I found the culprit. Where the concrete on one part of the dome base had settled unevenly there was a 1cm drop and as I had tightened the dome bolts to it, it pulled the walls inwards.

To resolve I unbolted the walls, put my foot on the offending side pushing it back in by 2cm and had Luke drill and bolt new holes. We then found some slate shims and shimmed up the part of the dome where the gap was. This fixed the problem and I now have a round rather than oval dome 😎

Next up was digging out the surrounding ground around the dome, as you can see here, the ground level on one side is around 4″ higher than the other. This would take some serious digging and many, many wheelbarrow loads of soil to moved.

Now was there time for rebuilding inside the dome. I found the control wood board and fitted it back in place. We fed through the electrical wire from outside to both the inside wall and the pier.

Bob then came round and did the honours of wiring the switches up, thanks Bob!

Now it was mount fitting time. 🥳

A few days later Luke and I performed the first fit, then I realised we had put it round the wrong way just as my friend Lawerence had done the day before at his 😳 so off it came again and we lifted it back on the right way round. That night was the test of how aligned were we to Polaris. Well it turned out not well enough. 🥺 I was off by about a degree. The MEII was at the end of its travel so I would have to redrill the mounting plate.

Another day, another task. The mounting plate came off, Bob and I drilled and tapped new holes to match where it needed to be and then refitted to the disc brake on the pier. We then hefted the mount into place and bolted down. That evening a quick test at night and the mount was roughly aligned very easily👍

Meanwhile I brought the ethernet cable in from outside through the conduit in the floor and fitted to the internal ethernet plate on the wall.

Next we fitted the SQM to the new fence post previously installed.

Followed by the All Sky Camera (ASC) and the weather station (AAG).

We then dug trenches for the cables and used some spare guttering to cover and backfilled with shingle overlaid with weed matting. Later we will place further weed matting down and add more shingle.

We then dug out some more of the soil to the side of the observatory and placed it at the front with a line of bricks to show where the step for the new patio would go.

The following day we brought in the 12″ OTA ready for fitting.

It was the next day after bringing this in that we noticed the water pouring off the inside of the dome and poling on the dome edge. The MEII was stoked and the OTA 😱

The dehumidifier was retired from the IMT3b cupboard in the workshop and installed! I also put a small heater supplied by Bob in the dome to keep the dew point down. Luke then helped me fit the OTA.

Like with all things the first fitting was wrong, I had forgot to reinstate the long 16″ Meade losmandy plate to allow the OTA to be gripped by all 4 thruster pins on the MEII Versa plate, so off it came again and then we had to find the bag of screws that fitted the taped holes.

Once found we refitted the OTA, placed the imaging train on, installed the Officina Stellare TC-04 controller for the OTA, fitted the Hi-Tec astro hub and balanced the scope. 28KG of weights were added and the telescope was installed.

Another day past and my other friend came over and helped install the Nuc, Mac, Raspberry Pi and the Intel Windows PC all to control the dome, telescope and various cameras and weather station devices.

Now the dome could be remotely controlled from outside 😉

Last but not least I installed the power for the mount after heading indoors to find the mount was not connecting.

I also installed the cameras for the North East and West positions in the dome to view the OTA in action and one on the end of the 12″ OTA to see where the slit is.

Then this morning I painted around the edge of the dome with fibreglass sealant.

I also noted the dehumidifier was working and nicely draining the water outside the dome.

Next up is commissioning the scope to get a T-Point, but here is my very blurry, not entirely correctly pointing first light image of an area of sky in Orion.

27th March 2021

Today was a big day. Not only was the plan to finish the concreting within the dome, in this case the pier, but also to bolt together the dome itself and get it fitted. The first port of call however, was to grab the newly purchased Land Rover disc brake that had been sprayed with 4 coats of primer by Luke and cut and fit threaded bar to it with washers and nuts to hold it in place inside the concrete pier.

We then drilled and taped holes in the MEII adapter plate that had served mew well sine 2008 when it was installed for the original ME.

Next we created a former for the slightly wobbly post next to the observatory where the weather station pole was to be installed..

Then we started to concrete the pier. After 1 load the pier was looking a little more full.

Then after 2 loads it was nearly there. With 1 more bucket of concrete it was ready for the disc brake to be fitted with the MEII adapter plate.

It sunk in very nicely and we aligned just West of North to account for Polaris. We moved the pier slightly to make sure the top plate was level.

Next the dome segments were prepared in the same fashion as the walls with electric sanding and then using mastic and bolting together.

Next Helen, Luke, Ezri and I lifted the dome onto the observatory base. Job complete!

Well almost, well not at all, there is still loads to do. Not only does the dome not rotate fully, due to the walls not being perfectly round (I need to resolve) but also the shutter drive needs fitting and the dome rotation drive and all the electrics and……. well you get the picture 🙂

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.