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Modified Metal Shed Observatory


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Part 1 - 'False Dawn'

So like most people in this hobby I would love an observatory. Never really thought I would get round to doing it though, so every session I rolled out the equipment, spent an hour setting up, then got down to imaging, then spent another half hour clearing up. So for a year or so I have taken the equipment from shed to the perfect location in the back garden for every session. I decided I needed a shed to store the equipment so I got one of those metal sheds and built it behind the garage.

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Now everyone knows how unpredictable our weather is, and how much time is lost in intermediate conditions when it’s a bit cloudy but not quite clear enough to expend the effort required to set up. Somewhat belatedly, I decided to have a go at an observatory. Or rather a run off bike shed.

At the same time as building the shed, I identified a site near the shed where I could see Polaris, still had a reasonable view south, and minimise the blockage from the garage. This was serious, so in the traditional manner a deep hole was dug to be filled with concrete for the intended pier. A run off shed was also found. I also laid some outdoor conduit for power, etc, to the garage.

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Well, the shed got built, but the run off shed never got beyond the hole and cable stage. I could never bring myself to get the shed, thinking it would never be as good as a proper observatory. I was also worried about security and environmental effects on the equipment. Another year passed, and although the metal shed was great for storage, the missed opportunities and time wasted made my mind up – a real observatory was required. But what to do? See part 2 as soon as I write it!

Edited by BlueAstra
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Hi Blueastra,

Nice job, will have given you plenty to do whilst the weather has been poor. Just a small point your power cable should be at least 600mm down and be steel wired armoured to comply with current building and wiring regs.

Its quite hard to put a cable that deep, I should know I had to dig a trench some 10m long for mine and it took longer than putting the concrete base in, what with hitting stone and old tree roots, some of which had to be drilled and split and the others sawn through.

You are also supposed to record the position and do the relevant tests if it is plumbed in to the ring main, but that is another story.

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Modified Metal Shed Observatory - Part 2, ‘Self Support’

Now you can see the obvious problem. The shed is already built, and in the wrong site. I’d rejected the roll off shed, and I already had a hole in the ground. Having a look round, the ideal new site was vetoed by management since it was in the middle of the patio. As described earlier there was a location just forward of the shed where I had dug a hole. So I could theoretically move the shed over the hole and take it from there. However, that plan was also refused by management in that it intruded too far into the garden. So could a compromise be reached?

I had a flagged area just in front of the shed, so I set up my mobile pier on the flags to see how far forward I would have to move to see Polaris (not absolutely necessary, I know), and get some view north. It turned out this was only one more flag away from the existing paved area. So if I centred the shed there things looked promising, since it was only part of the distance originally proposed. I finally got management approval for this, so the cunning plans were laid.

First step was to pave the area where the shed would eventually stand. Pre-first step was to fill in the hole already dug and remove the power cables. This was done and new paved area laid, complete with new deep hole filled with concrete (thank goodness original hole was empty!).

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Next step was move the shed. I sawed through the ground fixing bolts and rolled it forward on pencils to its new position. After kicking it back into a rectangular shape I drilled new floor fixings and sealed the base with bathroom sealant. I relayed the floor with the official observatory flooring mats over a damp proof layer:

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Now what? I reviewed threads on DIY observatories and picked up a lot of tips, but nothing that matched what I was doing. Most people do the sensible thing and design from scratch in a logical manner (prepare ground, dig hole, mod shed parts, build shed, enjoy the sky). I seemed to be doing it in reverse order in my madness, and I was quite rightly shunned by the community. And it was only me doing it.

So I needed a plan. This is what I came up with. Looking closely at the interior of the shed I noticed the roof was attached to a metal frame at the top of the side panels, and along a flat surface at the doors. So if you unscrewed the frame from the side panels, the roof was detached.

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However, the shed was ‘monocoque’ – unscrew part of it and it goes all floppy. So I needed and internal frame to make the shed self supporting with no roof. The top of the frame would also provide a base for the rollers. Hmmm, but how would I eventually get the roof moving and the wheels attached? My solution was to make the height of the frame lower than the side panels by an exact amount. The amount was such that you could build the roof frame on top of the support frame, and then by inserting a spacer (unused frame section) between them it would raise the roof high enough to allow the metal frame to be screwed to roof frame from the outside.

Wood was ordered and the internal frame built and firmly secured to the shed side panels. The frames were two rectangular section top and bottom, with vertical supports at the sides and corners. A problem was the sliding door, where a gap was required. The base frame had a section removed at the door.

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So that was the internal support frame built, and that’s were progress stopped as I pondered the roof solution and roll off support section. The saga continues in part 3.

Edited by BlueAstra
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Part 3, ‘Outdoor Support’

Before making the roof frame and tackling the problem of attaching the roof to it, I decided to make the run off rails outside the shed. The theory here was that they would be needed eventually, unless I went for the crane option, and it could form a working platform while working on the roof.

I decided to have two horizontal beams for the rails supported by four supports and two cross beams. I would mount the vertical supports in fence supports that can be bolted down. I needed to cut a hole in the shed to expose the internal frame and line up in the right place with the internal horizontal beam.

First problem was the metal fence post supports. They were for 50mm square timber, which I had ordered, but it turned out the timber was more like 46mm. So they rattled around the post support and had to be secured with spacers. Then much fiddling with spirit levels to get everything on a even keel. Everything was put together, and the posts were temporarily held in place with bricks.

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I then ordered two aluminium rails, L shaped, as a smooth track for the wheels to run on. These came in 5m lengths and had to be cut to length to fit. I then drilled and countersunk them for fixing points. The thought now was that I could also use the rails as datums for levelling the inner frame with the outer support frame.

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I slid the rails in and it immediately showed that the outer support frame was nowhere near aligned and level (with respect to the rails). Much undoing, sawing, and re-assembly later I had the rails flat and supported along their entire length. I also sawed a baton to the right length to act as a rail guide so I could use it as a gauge to set the rail width at any point. Somehow I also seemed to have engineered a downward gradient, but it wasn’t serious and I decided it would anyway help the opening process. At this stage I have temporarily held the rails down with clamps until I have the final positions (and the supports with bricks).

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There was quite a wobble at the far end away from the shed, so I decided to add a spacer between the garage and the rail vertical support on that side. This improved the stability no end and now there is virtually no movement in the frame. The timber was pre-treated, but I gave them all an extra coat of preservative.

Well, the stage was set. I now had no more excuses left for not building the opening roof section, in an ‘I’ve started so I’ll finish’ manner. The sky appears in part 4.

Edited by BlueAstra
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Part 4, ‘15000, Open Roof Doors’

Giving my age away a bit with that title, but how many of you know where it comes from? So the time had come to attack the roof. Following the plan I had built an internal frame, and an external support, and installed two rails (actually removed the rails for this part). The first step was to build the roof support frame. This was a rectangular frame, with corner braces, built resting on top of the internal frame.

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The next step was to detach the roof. This was straight forward down the sides, but the gable ends gave a little more of a problem. The gables screw vertically downward into the support rail at the ends. Undoing the screws was easy in the middle, but I had to undo the roof and peel it back to get at the screws in the corners. With the roof detached I then chocked up the roof support frame, which lifted the roof up with the frame. This exposed the metal roof frame resting on the wooden frame, and I was then able to go round and screw them together.

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I then attached the wheels to the bottom of the frame. I initially attached them at the corner brace position, but later I moved them so that I had four equal spaced wheels along each edge. The wheels are rubber and very quiet. I now re-inserted the rails and tacked them into position.

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So I was now ready for the first push back. I gingerly pushed the roof and away it moved along the rails. At this point I noted I had forgotten the proper end stops so after an emergency stop I put them on and did a full push back. This showed that the rails were accurate, but the roof did bounce sideways a bit as it travelled. To prevent this I mounted some smaller wheels horizontally to guide the roof along the rails. This worked really well, and the roof now moves smoothly back and forth. Finally, I added the traditional turnbuckle clamps to keep the roof on, with some extra hooks to secure it in the open position. I also need some hooks to hold them as the roof moves. I also added some cut rubber sheet to act as rain seals over the rails.

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I still have some finishing work to do, for instance secure the fence posts, make the door area more rigid, install some additional ventilation, but I have now declared the observatory operational! Was it hard work – yes it was, was it worth it definitely. Now all I need is some clear sky.

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  • 10 months later...

Part 5, ‘The Road to Oldham Pier’

The observatory has been in use now for the best part of a year, and I can honestly say it was one of the best things I’ve done in the hobby. I can leave all the equipment set up, and if there are any breaks in the cloud I can literally open the roof, switch on the equipment and be ready in about 10 min from leaving the house.

My setup was really my mobile setup moved into the obs, and left permanently connected. This worked well, but you had to be really careful in the confined space and darkness not to kick the legs of the support. This is a picture of the outdoor rig, which was moved completely indoors.

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I’d decided some time ago that I should install a pier to get round the stability issues, and make more space by removing unnecessary pieces of outdoor kit. I also decided that a refurbishment of the interior of the obs would be good, along with a general tidy up. I’d decided on the Altair Astro Pier since it was adjustable, a good height, and had a large top plate to accommodate any future mount update. I looked them up at AstroFest in February, but they had no show discount so I thought I may as well delay purchase until ready to install. At IAS I got a healthy 10% off and free delivery, so its good to wait! The pier arrived last week so it was time to install. I cleared the obs and drilled into the concrete plug to install the bolts. The pier then went onto the bolts to be clamped down.

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Since I had to clear the obs to do the work, I also decided to improve the wall and floor insulation, and install a ventilation fan to help out in the hot weather. I lined the walls with the same 22mm polystyrene panels that I had used to insulate the roof. The floor had a thin plastic damp proof membrane, but because it wasn’t insulated the cold flags underneath caused dampness under the floor mats. I got some thin insulated panels (for under wood panel floors) designed for concrete floors and laid then between the floor mats and the plastic sheet. In the following image you can see the wall insulation and the foil backed floor insulation with the first row of floor mats.

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Next is to move all the stuff back into the obs and look at attaching the mount to the pier.

Edited by BlueAstra
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  • 2 weeks later...

Part 6, Attempt to impress my Piers

I finished laying the floor and turned my attention to the pier and pier EQ6 adapter. I’d bought a pier adapter from BilletParts some time ago, and very nice it was. The pier top plate had a nice hexagonal pattern of clearance holes for the adapter, and the adapter also had a nice hexagonal pattern of clearance holes. However, it turned out the holes were on a different pitch circle so didn’t line up. I took the plate into work and drilled a new set of holes. I then took the bolts and lock nuts and tried to bolt the adapter down. The bolts were quite long, and two of the nuts locked solid before reaching the plate. They refused to turn and I ended up sawing them off. I then procured some shorter bolts and more traditional nuts and spring washers. Finally the adapter was on.

I levelled the plate, and watched fascinated how a massive steel plate and bolts can be minutely adjusted and then ‘relax’ back into position once the spanners are removed. Next came the EQ6 which was secured by a central bolt. I tweaked the levelling and then set to installing the electronics and cables. The gap between the pier and the pier top plate made a handy ledge for locating the 12V Stabilized supply, 12V distribution box, ZBOX Nettop computer, Dew heater control, USB Hub and Camera PSU. Everything is connected and controlled by the ZBOX, either directly by obs mouse/keyboard/monitor, or by remote desktop in the house via mains networking. After much deliberation I chose the fashionable ‘Rats Nest’ style of cable management. At least I can get at everything!

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I had decided to give the AG10 a refurbishment before re-mounting it. The first thing was to remove the primary for cleaning (yes, I really said that!). The mirror had suffered a bit during the winter with dew while ‘resting’, and it looked a bit dusty. I’d also ordered a metal ring to hide the mirror clips and reduce diffraction effects, so that needed to be installed. Finally, I wanted to stick some temperature sensors to the edge of the mirror to eventually work with my Ardunio based dew sensor.

The mirror was removed and carefully washed in soapy water, and cleaned with cotton wool balls soaked in the water. I finally rinsed it with distilled water. I followed one of the video tutorials on the correct method of doing this. After this the mirror looked brand new, and I then reinstalled it on the mirror holder. I attached the sensors with silicone gasket material and attached the new ring over the clips with velcro. Unfortunately the ring doesn’t cover the entire clip, so we’ll have to see how much effect it has (in my view the clips look a little too big). My other problem of the scope slipping down the mounting rings at high declination was address with more tape on the scope (super smooth felt in the rings on super smooth carbon fibre (ehh?).

I re-mounted the scope and re-collimated. This didn’t take too long at all. I then connected all the electronics, crossed my fingers and switched on. Everything worked!. I did have to redefine a lower park position since the scope was now higher, and the roof wouldn’t open. This all took place while we had the longest number of successive clear nights, so of course I’ve not been able to polar align or image anything yet. See you again at the next clear interval!

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  • 2 weeks later...

Part 7, Feeling a Little Flat

Continuing to commission the observatory. Latest addition was to test the flat panel system. This is a A3 electroluminescent panel set into a cut up thick cardboard box. The intensity is reduced with a white cotton sheet and some sheets of A3 paper. I cut a small hole in the rear to thread the power cable out. The box is self supporting, and sits nicely on the end of the scope. The power supply cable is too short though. I have to rest the PSU on the focusser to get it close enough.

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All this is controlled from Mission Control sat on top of my new storage cupboard. This is a plastic cupboard from B&Q, and gives me extra useful storage space (I previously had two big storage boxes that were inaccessible with the monitor on top. The keyboard/monitor is used to setup the scope and start a session, then control moves indoors via mains networking to keep an eye on things.

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I've also installed a B&Q mains bathroom extraction fan to help out with the ventilation during the hot weather (where?). This is controlled via a plug in thermostat which I've set at 30C. I've also tidied up the mains distribution blocks. One is permanently on for dehumidifier, security cam, fan, the other is switched when the scope is in use and powers all the other equipment.

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Finally, I've re-plumbed in the industry standard de-humidifier for observatories:

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Running out of small jobs to do now, hope that clear weather comes soon!

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Everything coming together nicely - good luck with the rest of the commissioning.

Quicky - how do you find the NEQ6 handles the 10-inch?

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I think the scope is about 12kg, and I have about 2-3kg of camera kit on it so perhaps 15kg in all. The EQ6 seems to handle it OK with 3 counterweights. Wouldn't want to put much extra on it. I didn't use an extension bar for space reasons in the obs. I would like to dual mount my other scope at some point ( I even have the dual mount bar!) but I think it may be a bit close to the limit. Currently thinking about an upgrade to handle this.

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