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This actually needs some explanation. In October 2004 when I moved up here the "garden" was best described as a mess. Having liked the challenge of astrophotography I decided to make a permanent telescope set up; very simply carrying all the kit out and up the steps every time I felt like a session was a pain. As you may know, putting it all together and aligning it is another pain, best done once and never repeated. Finally, being cold is one thing but being cold for hours on end is not fun, so there was also an element of protection to be considered. This is a project designed on the backs on envelopes and carried out by a man who has no training or common sense whatsoever. The fact that it all works should encourage you that it can't be that hard.....
Well it was a mess - uneven, rocky, overgrown, and accessed by steps built by the loser of the Design Stonehenge Competition.
It's more like a Spot the Garden competition really isn't it?
Having evicted a few pigmies, job one was to remove the tree, and see what was under all the growth. The land slopes from left to right, and from back to front. For fun, it's also tiered. The "soil" is actually mostly quarry waste, which consists of rocks too big to move by spade and rake, but too small to be of any use. Earth moving on this project was an absolute swine where brute force won the day. Job one was to rebuild the steps on the right hand side to allow safe access.
The plan starts to form
I realised that one continuous level would involve vast amounts of earth moving, and that the two tier system was here to stay. Wooden decking looked like the best way of getting a level surface, and seemed to be within my skill base. The idea was to box in the upper section, and initially I was considering filling it with top soil, but there was no way to reverse a truck up the drive, and lifting a ton of soil up 10 feet by hand was not attractive. Therefore I decided to deck the top of the box. Those of you looking will see that I have put some of the joists broad side up instead of narrow side. This was a major mistake......
The first take. Straight away three things emerged as problems. Firstly as I has been too lazy to put the joists in narrow side up, they flexed where not supported, and subsequently sagged in the centre. Secondly I didn't leave any gaps between the decking planks. Thirdly I tried to ensure everything was horizontal. Result: any rain didn't run off the decking, and pooled up in the middle. Hindsight is wonderful, but I should have deliberately tilted the decking to ensure water run off either to the left or right, and putting in my joists properly wound have provided proper support. When the decking was extended I lifted and relayed the decking planks with 1cm gaps.
Now we're off. I'll discuss briefly why I chose this set up. I've seen a couple of roll-off roof designs, and basically they were cramped with equipment, had compromised horizons, and you were still sat in the cold. It's the lot of the British garden astronomer - not enough land to build what you want. This design has its origins in a suggestion by Patrick Moore in the Observer Book of Astronomy of about 1968 vintage - the roll off shed.
The premise is very simple - the scope stays still, the doors open, and the shed rolls back to reveal the scope. As long as the doors are big enough it's a doddle. This is a 6' x 6' ground plan shed with double doors that are about 5' wide - on paper I could use my 12" Newt with its 48" tube with reasonable clearance. I had considered a minimalist approach of a rolling box just big enough to cover the scope. It could have cost as much to build as to buy a semi-fabricated shed, and in any case my neighbours at the time who I had previously been keen not to annoy, made themselves unpopular enough for any consideration of their feelings to be lost.
The cunning bit is this - once the shed is rolled off the scope, you then have a nice 6' x 6' warm room from which to image!
So the shed was bought on the www - it's a 6' x 6' design with double doors 5' wide. It took 4 or 5 hours to build. It came in prefab sections and the walls are tongue and groove rather than the cheaper wainylap type.
The eagle eyed might have noticed by now that just in front of the shed is a bit of concrete. This is 4 barrows of concrete in a hole excavated into the ground, and isolated from the decking itself by sawing through planks where needed. I thought about a pier then went off it - money and headaches stopped it happening. Here's a better shot:
Rolling, rolling, rolling!
For a brief while I simply kept the scope in the shed and lifted it out onto the base when so required - it saved some time setting up - but the real challenge was to get the shed rolling. It's at this point that there was some experimenation. Without going through all the failed bits, I ended up doing the following; basically sheds are not meant to move once built and the structure flexed badly when moved. Therefore I used 3" square tanalised timber to build a u-shaped frame on which the shed now sits - the door side of the shed is the open side of the u if you see what I mean. With hindsight I should have also braced all corners with some plywood web to hold them all square but never mind. The rolling element was provided by 4 2" non-castored wheels from the DIY shop - £3 each. I laid two strips of tanalised planking for the wheels to run on, and made guide rails from 1/2" square dowel to ensure the shed rolled in a straight line and also didn't spread as it moved. Here's a roller under the 3" square beam:
Obviously this now left the shed 4" or so higher than before; the solution was to attach some plank skirts on the outside, and the final 1/2" gap was filled by stapling some black plastic refuse sacks to form a flexible skirt inside the wooden planks. It keeps the draught out very nicely.
Here's the heaving strap on the rear:
Does it work?
Well yes it does. The shed can be rolled off one-handed on a good day, and with the guide rails it will roll easily back into place for locking up. Yes there is the odd trickle of water every now and again on the floor but I have made a rudimentary forced circulation system - a fan heater on a low setting at floor level, andf a PC cooling fan at head level to suck warm air out of the shed. The mount and scope don't get damp, and I can turn the power on and off from the house - it's as easy as that.
There's plenty of clearance with my normal imaging set up as the shed rolls off, and room inside for a table and chair for when imaging. A few hooks and screws inside to hang heaters and cables off keeps it tidy.
This is how it is when in full operation. Control cables and connections to camera etc run under the door quite smoothly as long as I check that they don't snag or get overtight as the scope tracks. You can also now see that the decking itlsef has grown a balustrade and a nice swinging chair - by happy accident I've ended up with a very nice extra bit of sitting space right at the back of the garden, with a big iron chimneyburner thing that is also a barbeque - very nice for summer!
Now compare this to what we started with.
The wonders of hindsight
It's fair to say that for less than £500 I've a good observatory that keeps to what there was a of a design brief - it's a secure dry place to keep the scope set up to reduce faffing around setting up.
The isolated concrete base works fine - I can walk around, etc, with no effect on the scope. I have put a massive square rock under the tripod to make sure it's as heavy as possible The shed serves as a very comfortable warm room when imaging - it is easy to keep the temperature 12 degrees above the outside temperature, and this comfort factor is important as I am manually guiding my exposures still. I've used some left over foil coated bubble wrap insulator and polystyrene tiles to add insulation - not obligatory but I had the materials going spare.
It's roomy enough that I can sit in the shed with the scope inside to do maintenance etc. As a concept I would thoroughly recommend it over roll-off roof designs or classical dome types. Working with wood is great - you can't use too many screws and it's all very user-friendly and quite light to boot. I've given it two coatings of a green tinted wood preserver to tone it down a little, and also doubled up the tar paper on the roof - cheap to do but worth it for the long run.
There's mains power obviously, and I have put a light in the celing, and also a bulkhead light in the rear wall to light the decking area for summer evenings sat outside.
However with hindsight, if you are thinking of this design there are some considerations:
you need an area at leat 6' by 10' for the shed to roll back in. In an established garden this may not be easy
you would be well advised to build a very very level base for it to roll on and off - I have to push it off slightly uphill but I'm a big lad
the area around the base should be slope so rain runs away from the shed - not under it as mine does
two roller wheels per side is the minimum - I'd recommend three or even four to reduce rolling friction, and ensure axial stability
I would build the u-shaped base fram base out of 4" square timber and brace the corners with plywood webs to ensure it stays square
I would also internally brace right angles where possible for the same reason - it's not a problem that the shed can flex, but better if it didn't
check your set up will pass through the doors - you may need to have the shed roll on a certain axis if you have a big scope so it fits the door
The bottom line - it works for me, wasn't too difficult to do all in all, and if I had to start again afresh, I'd do the same thing again, with the improvements as per the above points.
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