My astronomy project:
Making of a concrete pier to the mount
1: Introduction and steel plate
Who is the person who don't want a permanent observatory? With a observatory you can leave parts of your equipment in place and have a polar aligned mount ready for astro photography.
I already have the EQ6 mount and had drawing some planes how to mount it on a self made concrete pier. I started with the steel plate that will connect mount with the concrete pier.
I was lucky to find a workshop that could manufacture these steel plates, I made two of them.
If you live in Stockholm (Sweden) you can call Eje Eriksson at this company and ask if they could help you:
They had circular steel discs laying around and was able to drill the holes I needed. It should interest others here too, the plates they had has dimension 21, 25 and 28 cm in diameter if I remember correctly, and there was some up to half a meter if you are plane to build something really big.
They can essentially weld anything if you have special needs. I chose the size 25 cm in diameter and 12 mm thick. Little bit to big for my EQ6 mount. But that leave space to mount a EQ8 when I get tired of my EQ6. Note that there is a small notches in the edge of previous cutting but it doesn't matter. I placed my holes very far out on the edge of the possible because of future EQ8 demands. There are three 18.1 mm holes and in the center a 12 mm. Later on, I also drill a hole and thread for stop to the mount head.
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2: Making of the two concrete piers
Has now come a step further on the making of concrete piers. Two piers will be made, they will be placed about 10 meters apart. One will be used for photographing, the other for visual use. When the opportunity appears a binocular of about 20x100 mm with angled eyepiece will be purchased. Shooting will take place the more or less automatic so then it's nice to be able to sweep across the night sky with binoculars and look for beautiful objects.
The reinforcement for the concrete pier is made of three pieces, drilled holes in the rock.
This is the threaded rods before they become embedded in concrete. I chose the dimension M18 and about 60 cm long, they also reinforce the pier. The rods are slightly bent inward center so it becomes more concrete around them when I did not want the pier to be wider than 25 cm. Someone here mentioned to me that it can be a problem that the equipment can collide with the pier in certain positions.
The bottom of the paper tube is already filled with 10cm concrete, now I install the steel rods. The slope of the plate is adjusted carefully in with spirit-level, afterwards when the concrete has burned and sat I fine-tune it with the nuts at exactly the horizontal plane. The steel plate must sit further down later so that the threaded rods are not wobbly.
Here are the concrete burned so that I can take away the steel plate that fixes the threaded rods. A small hill has been built on top so water will drain away. Actually, my first idea was that a drain pipe would be cast inside the pier where cables could be drawn, however, I was a bit worried that it would be formed pools of water in the winter and the risk of freeze damage. Five 25kg sacks fine concrete was spent on the two piers and it is a long steep road up to the rock top!
The assembly of EQ6's bottom is not flat and a spacer with hole diameter of 65mm must be manufactured, at least 20mm thick. On the picture you can see how I solved the famous problem of EQ6's, the power cable that jumps out, I have solder a new one directly onto the circuit board. The first cable cracked out in the cold and now replaced by one of better quality. It's partly twinned to reduce electrical interference.
A guide pin must also be installed in the north direction on the steel plate when I have measured out north direction more accurately. The guide pin becomes an M10 bolt threaded on top, a total of three M10 bolts will hold the spacer in place. I chose to turn the plate so that one of the bolts ended up in the direction to the south. Thought it seemed the best at that time, now I feel it is better if it had been pointing in north direction. No problem, but had become a little more room around the adjusting screw for the altitude adjustment. Here in Stockholm we live on the 60 degree latitude and normally I use only the north screw adjustment, the south will in such an oblique angle that it risk to bend. There is modification kits for this. It doesn't matter how you turn the steel plate, the adjustment bolts will always collide with something, this seems to be a big problem in the future, maybe I make a new steel plate with welded bolts, that gives a free plan surface for the mount head. But now I am most eager to give it a try.Back to contents
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3: Assemble it together
Struggling on here with the pier construction. Inexperienced as I'm in this, it will be one or another mistake, read below.
Here we have dragged up the equipment up the mountain. A steep hill up to the top but there are some staircases made of stones that help. But the view from the top is really impressive so it is worth it. Before assembly mount and the steel plate on the top of the pier was painted. My handy girlfriend takes care of it, we choose a color in white. I thought it was a good choice but it turned out that already after one day we had a steel plate with rust. Have to grind it down and put some anti rust paint first, mistake one.
Here you have the color before the rust and it looks really neat out. The white ring on the top is a temporarily disc made of wood. Thought it was best to make a sample before I order one in steel. Usually always be something you overlooked. Then when the exact north direction has been measured out I drill a hole for the azimuth adjustment pin and mount the M10 bolt.
Here is the mount head in place. Mistake two was to turn the bolts so one ended up facing south. Luckily it was no problem for me with this EQ6 mount head. Both polar scope and altitude adjustment screw is free from hitting anything. But with a different mount maybe it could be a problem. Actually quite easy to fix, just do the spacer plate thicker.
Mistake three was not to examine the rock properly, it turned out that under the moss it was a big hole in the rock where water collects. Must dig it out and filled up with stone and then maybe a concrete layer over. Now there were not so many other good places for the concrete pier so it had ended up here anyway. There are small channels for the water to escape in any case, so the water drains away quickly.
Later when everything is tested, the steel plate is moved down an inch or two so that eventually any wiggling in the threaded rods are minimized. They may also be cut so that no unnecessary parts stand up posing a risk of telescopes and cables. Advice from others are to use M20 rods to be sure of a steady.
The total weight:
I learn from my mistakes :-) and I share them here so others can avoid them.Back to contents
4: Find north and level mount
The construction is advancing further from steel plate to the pier and now a first test. The goal of the evening is to find the north so that the hole for the stop bolt can be drilled and mounted. There is a stop bolt adjustment screws on mount head that takes support against this stop bolt when adjusting the azimuth (lateral).
Starting with angling down the RA axis so I have some distant treetop to aim for. Twist round RA 180 degrees to see that the reticle in polar scope points to the same object. Yes a little tricky when the wind blows and the trees swaying side to side. But it went well in the end and it was already aligned close to perfect.
As is known, the polar star does not end up exactly with the Earth's rotation axis extension, but close to one degree. You should use the North Star as I am now, before I make a more precise drift align. Perhaps I'm most curious about how good it is. For this to be good must be engraved ring in polar telescope be rotated at the same angle as the stars at the time. Reading the manual for EQ6 and I'm is close to falling asleep by the boring text, all these scales must be turned from here to there. I choose instead to use the control program EQMOD that I use for installation. But first, are there other adjustments that must be made.
The toolkit for the evening, especially the spirit-level and the wrench for fastening bolt. The rain protection to fast protect the telescope in case of rain, i live in Sweden! The wagon is of great help when the heavy equipment must be taking up and down the mountain.
First adjust the steel plate so it is in level with a spirit-level. Here we see that the integrated spirit-level is not of good precision.
The next step is to adjust the RA axis, it also adjusted by the spirit-level, find where the horizontal angle is. Sets the RA scale on 6h, then turn the RA axis to 0h. It is difficult to find a surface that is parallel with the RA axis to hold the spirit-level against. I hold this spirit-level against the shaft where the counterweights are placed.
This spirit-level worked well but later I will attach other permanent so I get a built-in spirit-level to adjust axis with. Need surely to do this several times if the motors loose there position, then I want it to go easily and quickly.
The next step is to adjust the Dec. axis, do the same here. Finds the horizontal position with a spirit-level and set Dec. scale to 0 degrees. Then rotates the Dec. shaft to 90 degrees.
Now I have reached the point when to start peeking in polar scope. Steering controls from EQMOD and set Dec axis so polar scope can see through the bore in the shaft. There is a special routine in EQMOD for polar alignment, choose the position at 6 o'clock. It is intended to be able to select various modes to avoid Instrumentation hit mounting. In my case, I have nothing that stands out so it does not matter.
Adjusts the mechanical assembly in azimuth and altitude so Polaris sits on the cross. Then I adjust the latitude so Polaris sits on the circle in the 6 o'clock position, i.e. straight down. Now I run the engine in RA axis until the small ring at the major points in the middle of the North Star.
The next step is to store the position in EQMOD, then give the command so that mounting turn the RA axis so that the selection in the polar telescope is true for the North Star at that time. Adjusts now once again the altitude and azimuth to the North Star, now this time end up in the ring in the circle of the polar telescope. I have now if everything went right a rather precise position for north direction, a magnetic compass is not good enough. I later take a few test shots to see that the direction is indeed right before I drill the hole for the stop bolt.
So here's the stop bolt fastened. It is an M10 bolt with a nut on both top and bottom, to be able to adjust the height. Shall later make upper part on both sides flat against the adjusting screws.
A temporary spacer is made of a wood so I will be able to do some test before the steel distance is manufactured. A hole has been taken up for the stop bolt into the distance and a recess for the nut.
Put on the camera and doing some testing, pointing quite wrong, but it is a 165mm lens so not so sensitive to pointing error. It is a Pentax 6x7 with over 80mm in both the back-focus and image circle and wonderfully low vignetting. The opening is f2.8 but I normally use the f4 setting.
Here is the guide telescope mounted, a 400 mm camera lens with a QHY5 CMOS camera attached. Later the guide camera shall be connected to an off-axis adapter mounted on the main telescope.
A lovely warm evening and the observatory's control center could be moved out and I got closer to run up to the mountain. Yes, it was so much running running up and down between the laptop and telescope. All connected over a network and the telescope have a server computer that is remotely controlled by VNC. Normally I have a 24" screen to the laptop where I control it from, work very well. Although my computer broke down one night later. But the astro server continues to work regardless of what happens with other computers, and continue to shoot astronomy photos.
It took three days because of the clouds came and went, yes, most came. Rain protection came in handy as a protection to the telescope, under the blue bag is the server computer and the battery that I wrote about in another project.Back to contents
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One thing left to do is to drain around the pier. As you see that under what I thought was a thin layer of moss there was a hole in the rock. I must have it drained and dry in the surroundings of the telescope. Maybe not so serious problem, most built there observatory on lawns and it works that too.
This how it looks for the moment, rock edge has been removed. Has been relatively simple, with chisel and hammer. Did not know astronomy include this kind of job, but you get good exercise.
To the right stands the water. Luckily there is a crack in the rock that after processing can lead the water out.
Here are the channel to divert water away. Has lowered the ground 0.1 meter so that drainage will be effective. The remaining cavity fills up with crushed rocks.Back to contents