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Nerd Shed Observatory Introduction


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Hi All,

I thought I would share my labour of love over the last few months... I say a few, ground was broken in April and I had my first proper night under clear skies with it on Sunday night, so maybe more than a few months!

Apologies in advance it is hugely picture heavy, so I'll add a little summary now and let the pictures explain the rest. It is approximately 2.3M diameter and about 2.45M high. Built closely following the "How to build a home observatory" guide on the BBC Sky at Night website but with one or two tweaks and changes. I went back and forth between a roll off roof shed and a traditional observatory design and just liked the idea of the traditional look, but I wanted a little extra space to hide things away and help overcome a bit of the limitation of the circular shape, so added a little "nook". A 50W solar panel just keeps "critical systems" running when not hooked up to mains.

It is a manual shutter. Again, angst over that for a while, but a mechanised shutter was going to need to be in two parts and potentially quite noisy for the neighbours when closing up at whatever time in the early hours. It also kept the build marginally simpler and is light enough to pretty easily slide on and off as needed. The dome itself is motorised using a little arduino, and a fairly heavily modified version of the "/juanmb/ArduinoDomeController" found on Github : effectively modified to use a stepper motor instead. This works very well  and simulates the MaxDome II protocol so can use its ASCOM driver with N.I.N.A for autonomous control. 

There were a few challenges along the way, May, and its weather especially but really pleased with the way it has turned out and the way it is working. Minor issue with fairly considerable condensation forming on the pier and sometimes the mount but hoping some soil heater pipe around the pier will help, I guess just being the biggest lump of metal it will naturally be a cold sink but it needs sorting.

The mount is really interesting. We have had it in the family 20 or so years. It was bought via freeads (who remembers that! an actual paper you had to buy from a shop containing categorised adverts you had to trawl through!) and we (my Dad and I) added a Sitech Servo system to it. That only very recently has failed, so has now been replaced with an OnStep DIY stepper motor system which I have to say, I am very impressed with (it even has a build in wireless server, so no control cable needed). We aren't at all sure of its background, but it looks strikingly similar to some of Rob Miller's creations and the Astro Promotions PM1 mount. Its BIG though, having a 9" 180:1 RA worm wheel in brass and a 6" 180:1 DEC wheel in brass. I'd never want to get close to testing its payload limits, but it came equipped with 34KG of counterweights, so I'm thinking its capacity is pretty generous.

Modern times are great! The obervatory PC is an intel NUC mounted to the telescope, which means wiring is super neat, with just one power cable up to the telescope itself to worry about. I remote into the NUC using my laptop and control things from there.

It is very early days, a slightly frustrating first night on Sunday due to Bluetooth and battling Windows power management. The dome is Bluetooth controlled, but Windows puts the bluetooth to sleep, which then locks up N.I.N.A, which then means bye bye imaging run and at 2AM that is a reasonable signal to call it a night. Sorted now through various registry tweaks - if anyone has similar issues let me know and I'll post details.

Thanks all!

Getting the main ballast hole dug along with the outer pad stones. 




Threaded rods for concreting in and bolting the pier down onto along with the main outer structure cobbled together. The cage should (I hope) add some reinforcement to the concrete but is not strictly rebar, it is one of those cages meant for putting stones/rocks in and building up walls or rockeries.



So much cutting! Any normal person would have used a router and a circle cutting jig. I did try this but the bit kept working loose in the router (probably user error or a worn collet) and didn't fancy that spinning up into my face so moved over to the jigsaw.


Now starting to draw interest from the neighbours, main dome structure completed. This was around the end of April, then May hit and we had rain pretty much for the entire month!


This was my damn you May weather tent. A temporary structure built to house the dome for the rest of the build.


This was a Jaws'esque "we need a bigger boat" moment. I bought the pipe on the left based on my Vixen GP mount, around 140mm diameter thinking that would be fine. Then got the measurements for the mount that would be being fitted, 300mm base! The pipe on the right is 240mm diameter, 7mm thick. You may recognise the colour if you do a lot of motorway driving - its an offcut of one of those poles used to support the "Don't Drink and Drive" signs. I do have another two peices left, each around 1200mm long if anyone is interested.


Concrete going in. I was kindly loned the use of a cement mixer... which failed about a 1/3rd into the job. By that point I had to carry on so I became the power behind the cement mixer (they are surprisingly efficient at mixing concrete, so still easier to do that than mix it on a mixing tray).


Subfloor in and the outer bottom structure getting completed.



This was just a test of how well the 3.6mm plywood you can get would bend around the dome structure... very well it turned out. I think the trick is to "fair" the curve as best you can (I think its a boat term, just means an even curve with no bumbs etc). The plywood then just needs clamping either end and sits nicely to the ribs.


Floor in and bottom plate for the pier drilled for the threaded rods. You can see the conduit for the cable runs, in the end mostly unused other than the 12V power cable. For the most part it is all 12V other than a few mains sockets in the nook.


The one thing I thought I would really miss was, in the middle of the night dropping an eye piece cover or other small thing in the grass and never finding it. Wanting to retain that experience, fake grass was fitted as the floor surface. Primarily, I am hoping it acts as soft cushioning in case I do drop an eyepiece, but also as a bit of soundproofing just to keep any disruption to neighbours down, the houses are all fairly close. IMHO I think it works quite well.


Bench test of the dome controller. This was when I was still debating a mechanical shutter hence the second motor controller. As you can see, not much too it!


This ended up being slightly inspired. Corrugated cardboard was used for the templates. It worked really well, being corrugated, it only wanted to bend one way, which you could use to simulate the way the plywood would bend. It was dead easy to clamp an oversized bit on, draw around the inside of the ribs, account for the rib size and the templates were spot on.



Too many boat repair videos watched! The skins were glued on from the inside using fillets of thickened epoxy. This meant you could take your time clamping everything up and aligning nicely before then applying the glue.





The seems/edges were all filled with thickened epoxy, then fibreglass taped over. At this point, I was still playing with the idea of keeping it a natural wood finish with yacht varnish.


Sanding, oh glorious sanding! That will be the takeaway from this project and the dome specifically I think, so so much sanding.


First coat of the Dulux 3 part "system". Part 1 is I think a con, its basically boiled linseed oil sold at a premium.


Primed, 2 coats of the most uncooperative paint I think I have used. It better be worth it, supposed to be 8 years.


Its on!


Shutter being built around the main opening. I was keen to keep the shutter skin all one piece to minimise plywood edges.



The edges of the shutter and around where it slides were coated in a "special" tape. It is 3M poly tape, and I couldn't believe the price when I saw it retail - its over £1200, for a roll of tape! I still don't understand that, but suffice to say £25 on ebay and a few days later a roll arrived. To be fair, it does seem good stuff despite being just sticky backed, thick pastic bag. It stops the gloss on gloss contact and makes for a very smooth moving shutter.

Actually, to the point where I used it around the outer edge of the support ring that forms the top of the octagonal structure, and it acts as a bearing surface for the main dome itself - the bottom skirt effectively rubs along it. Dead simple.


Rocket pier prepared ready for welding, something I had never done before so a little apprehensive. 


Second ever weld trying stick welding, pretty happy with that, so a bit more practice and the pier was welded up.




I learnt the hard way, never ever break a tap off in a critical piece of work. This was when tapping the holes in the 15mm steel top plate of the pier for the mount. This is a picture of it half way through drilling it out. Diamond tile hole saw bits were used to drill around the core, which luckily then just dropped out the bottom of the hole, leaving enough "meat" to finish, carefully, the tapping.


About an hour and a half, and many diamond hole saw bits later! The tiny core from the broken tap can be seen on the left, so much fuss over such a tiny thing!


Lighting and general wiring. There is a white light circuit comprising 4 LED strip lights, and a red light circuit comprising those fake EL light strips with LEDs in, which actually work really well. Both are independently dimmable and switchable. 


Everything is independently fused. 8AWG main supply and then 10AWG for the main branches from there (lighting, mount, telescope etc). The insulation is just an attempt to keep air flow to the bottom of the pier from under the observatory down, hopefully reducing the cooling effect and condensation.


Lighting. The red glow is the EL LED strips, very effective when dark adapted.


"Operations" area. The solar charge controller, mains plugs and 12V/30A power supply are housed here.


OnStep controller completed. This is the STM32 Blue Bill version using TMC2209 stepper driver boards.


Still some wiring (USB cables mainly) to complete below but the general impression is there. Its an Explore Scientific 102 FCD-100, with an SXVR-694... one can definitely not blame his tools!!


A few of the mount prior to moving to the dome, compared to the Vixen GP for context.




And one quick shot of the Horsehead and Flame taken on the Sunday. It was meant to just be a night to get polar alignment nailed, but I got carried away. Just 7, 3 minute frames through an SVBony 7nm H-Alpha filter... before Bluetooth went to sleep and locked up N.I.N.A :( The OnStep controller is working well.


A few little videos, one of the dome seen moving from the outside, and one of a slew and the dome following suit.


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Wow, what an absolutely incredible build! I really enjoyed reading your post. Amazing craftsmanship and skill has gone into that, you must be delighted with the results! The mount looks the business too. Hope you have many happy hours in there 👍👍

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An absolute pleasure going through your build process. Usually I would just scroll down to the pictures and see what someone has done but the entire story was a journey. To top it off, what beautiful skills you have and the end result is jaw dropping gorgeous. 

The pier looks like a complete beast. Not sure whereabouts you live because if any closer to London, I would pick that pier off you in a heartbeat. 

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Thank you all for the kind comments. 

Alan the "Wood Butcher" comment made me chuckle. I went into this having a reasonable amount of practical DIY knowledge (did up my house) but for the most part it was learning new skills. There was lots of try something, fail at it, come up with a different approach and try again. If I ever had to do it a second time around it would probably take half as long, but building a dome feels like doing it once in a life is enough :) Now its complete though I am really pleased - my Dad said a bit like climbing a mountain, remember to look back occassionally at how far you have come.

I am down in Poole, Dorset if that is local enough for anyone that would like the other bits of the pole. They aren't completed piers though, just the rough cut bits of pipe that you would need to then fabricobble the rest together to turn it into a pier. Oh, what I did learn from the pier is my ability to estimate volume is awful. Its filled with kiln dried sand, after it was welded, through a 25mm ish feed hole in the pier top plate. I drilled a similar sized hole in a bucket, put that on top of the pier and then fed sand in through that. Quite theraputic watching the sand dissapear from the bucket.

I'd bought 6 bags of sand thinking may need more. Half way through the 3rd bag the bucket stopped emptying! Now I have 3 spare bags of kiln dried sand to distribute around the garden perhaps in a Great Escape esque style.






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On 11/11/2021 at 13:04, VaguelyAmused said:

Thank you all for the kind comments. 

Alan the "Wood Butcher" comment made me chuckle. I went into this having a reasonable amount of practical DIY knowledge (did up my house) but for the most part it was learning new skills. There was lots of try something, fail at it, come up with a different approach and try again. If I ever had to do it a second time around it would probably take half as long, but building a dome feels like doing it once in a life is enough :) Now its complete though I am really pleased - my Dad said a bit like climbing a mountain, remember to look back occassionally at how far you have come.

My Wood Butchery is often a dource of amusement to many.

At school my much admired Wood Working teacher told me one day, for all you best effort Mr White, you are a certified Wood Butcher,
do me and timber a favour and never try to become a carpenter..... and he was right.

I am ok at first fix type work and DIY generl wood, but anything like finsihed and showing wood, well, best left alone.

On the note about your Dad saying about to look back occasionaly, wise words of wisdom indeed.

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Really beautiful job Vaguely :) There’s something special about domes and a hand made one is really special. I was at the Royal Greenwich Obsy a couple of days ago and they said the original dome skin was made of papier-mâché! If i ever get somewhere to build an obsy, i want to do the same ;)


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