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Retrofit Concrete Pier Into Observatory

A while back I installed my NexDome Observatory onto an elevated decking. This was done to clear bushes in the surrounding area. Despite building a really strong decking, there were still issues with micromovement detection.

I do a lot of the imaging remotely, from inside the house which did help to some extent. However, I do still like to livestream and generally tinker around in the observatory. This resulted in my movements being detected by the scope (which is sat on a tripod on the decking) and causing bad exposures.

Despite the decking being really sturdy, even the act of lifting my arm was enough to be detected in the guiding. Ok, so I remote in to the observatory for the long imaging session, solves the problem yes? No, unfortunately not. Even when I have not in the dome, during imaging sessions and scope is tracking the sky, the dome has to slew round to keep in sync with the telescope. This slewing of the dome, could also be picked up on the guiding, although it was slight and only for a second, it was enough to annoy me.

I took the decision to retrofit a pier into the dome, and fully isolate the scope from the dome and the decking.

I documented this project as it unfolded over the course of a few days and you can watch along in this video;

It all started when I was round at a friends house, and when I was leaving, I noticed at the side of the road buried in some scrub land bushes, a discarded length of uPVC drainage pipe, so stopped the car, climbed into the bushes, hopefully not encountering any spikey things or snakes, pulled it out and loaded it into the car. I didn't know how long it was, but it looked good. With the pipe running down the inside of the car, from on the dashboard to all the way to pushing against rear tailgate.

Getting it home and taking a closer look at the pipe, it was 2.67m, 7mm wall thickness, 200mm diameter uPVC. Nice and sturdy. Out with the tape measure and doing some height checks in the dome, and under the decking and I would be able to use this pipe without cutting it. All I would need to do is vary the depth of any support hole to accommodate it.

Next up was to dig a whole under the deck, armed with a small shovel, scraper and a battery drill which had a slightly bent wood spade bit I started to dig, after first cutting back the moisture barrier and weed control fabric in the relevant area when the pier would sit.

After a few hours I was down to depth of around 82cm, the battery drill with the spade bit on it was the winner in this, as I was able to chew up the soil to make scooping it out so much easier. The depth of hole was eventually limited by my arm length, so was glad to find that that was a suitable depth. No frost line to worry about here in Cyprus, so the depth was more than adequate. I undermined the lower half of the hole to open it up a few centimetres compared to the top of the hole.

Next, I cut an oversized hole in the decking, around 220mm in diameter.

Opening the dome shutter and rotating the dome, I proceeded to lower the pipe through the dome and down into the hole.

After checking for level I temporarily secured the pipe vertical with small L brackets screwed to the deck.

Next up, I mixed cement and filled the hole around the pipe. Leaving it to set over the next 24 hours.

I purchased some M12 meter long steel rods which would be used to anchor the pier head I had (a Baader Short Pier). This would also provide some reinforcing to the concrete.

Below you can see the M12 rods, tied together at the bottom to form a spike I could drive into the wet concrete was poured into the pipe.

Next Up I put a layer of gravel at the bottom of the hole, around 6" or so. This was the view down the pipe before the gravel was tipped in.

Mixing up the concrete, and filling the pipe, I then pushed the pier head and attached M12 bars/spike into the pipe and sat it on a cross bar support and left it to set for around 48 hours.

After it was set, I removed the pier head, removed the temporary brackets and refitted the temporary flooring in the dome, the flooring was some old swimming pool liner. The centre hole I cut out of the liner, was fitted onto the top of the pipe and acted as a separation layer between the concrete and pier head. I also cut a number of fingers all the way round the flooring to cover the hole cut in the deck, but maintain separation from the pier.

The pier head also had 3 additional M12 threaded holes for fitting of levelling bolts.

I put the whole lot back together, and setup up the levelling and bolted everything all down tight.

It was a case then of rebuilding the telescope rig, starting with mounting the CGX-L mount onto the pier head, then attaching the Celestron RASA11 to the CGX-L, and connecting up all the cabling.

After this cabling was done, I did a rebalance of the rig, and waited for dark to get the polar alignment done and test out the difference.

And there we have it, project complete! What a difference it made, everything is solid, no movement when in the dome, not dome rotation detection in the guiding.

The only change I had to make was to the dew shield, as the slight increase in height of the pier was escalating the already collisions I was seeing with the Dom shutter motor box and the dew shield. I simply cut back the Dew shield 6 inches, and now no collisions.

I really could have asked this to go better. So please with the outcome.

Not having the tripod in the dome has also added so much more room in there. And now I will be eventually able to get a decent chair to sit on as no tripod legs in the way. At the moment I was sitting on some polystyrene blocks that the mount was shipped in, but this was giving me sore back and neck if sitting for any length of time.

Next up, build another pier outside the observatory for Rig #2!

See the video for more detailed run though and of course there is lot more content and imaging sessions on my Youtube Channel.

Until the next time,

Clear Skies!

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