The roof would be cut in half at the middle along the minor axis.

Four wheels would be attached to each section of the roof making the two sections moveable independently of each other, in either direction.

Both sections of the roof would be padlocked into place when closed.

The pier mounting would be bolted to a concrete slab.

The rest, we made up as we went along.

The roof was originally mounted to the walls with pop rivets. These were easily removed with an electric drill, and the roof removed. It was surprising just how flimsy the roof was once removed and it was immediately obvious that structural reinforcement would be necessary. For this we decided on 50x50x3mm angle iron for the roof trusses. Also for structural integrity, 3mm steel plate was used for the wheel brackets, which were welded directly to the roof supports.

The wheel brackets and roof trusses of the innermost roof sections with the roof closed. One of the three roof padlocks is also shown.

All steel was cut to size on site but we did not have any welding facilities. Remembering an advertisement from television where a small hand walks around looking for things, Mick found a mobile welder in the yellow pages that actually made house calls. He came over and welded the lot for $50, took about two hours and did a great job.

As with most roll-off roof observatories, a track was required for the wheels to roll in, and guide the roof sections when moving them. C-Purlin is often used for this purpose and come in standard lengths of six metres, which is perfect for a 3-metre shed, allowing for 1.5 metres out each end, for the roof halves to roll out on.

The purlin, wheel bracket and roof truss for one of the outer corners. AOne of the C-Purlin sections B The wheel bracket is joined to one of the outer angle iron roof trusses. Note the hole cut into the wall to allow the purlin to extend out of the shed. C The outer angle iron roof truss bolted to the outer edge of the roof section, with rubber flashing riveted to the other side of it. D 10 x 40mm ply support. This is bolted to the shed wall from the outside, and to the purlin inside. The ply also holds the shelf support chains. E A wheel.

The original plan was to bolt the C-Purlin on the uppermost edge of the walls on the outside. But we soon realised that because the doors extended all the way to the top of the walls, we could not do this and still expect to open the doors. So the C-Purlin was positioned on the inside, with slots cut out of the end wall corners to allow the C-Purlin to poke out through the end walls. This has the added advantage of keeping muck out of the C-Purlin, by having the majority of the exposed track inside the shed. There is a slight disadvantage of having to cut slots into the walls, which could allow wind and rain into the shed, but after several bouts of heavy rain, it seems to be coping well.

To keep the weather out of the gap between the to shed halves when closed, two lengths of galvanised flashing were purchased from Mitre 10, and with a little retro-fitting, mounted to the western side roof half, so as to cover the gap. This is shown below. As an extra precaution against water leaking into the gaps during a heavy rain, several layers of adhesive rubber strip were placed along the entire length of the inner roof truss of each roof half.

Lastly, the concrete slab for the pier, (my first slab) was a 30x30x30cm cube made with 90kg of pre-mix concrete. The bolts to mount the pier were bought as a single threaded bolt, 1 metre long and cut into 4 pieces. I first thought of doing this with a hacksaw, but after making my first 1mm dent in the hardened steel, realised my blatant stupidity and let Mick use his angle grinder like he suggested in the first place.

Masonite was used to minimise vibration through the floor to create a gap between the surrounding earth and the outer walls of the slab. In hindsite, rubber would have been better, but the masonite is better than nothing. The jumping test still causes significant movement in the scope. So if you come around, please remember, no jumping in the observatory.

Enough of the bolts were left protruding from the slab, to allow a nut to be placed both above and below the pier base plate, to allow for levelling the pier. This has worked well and greatly simplified the process.

240V AC Power to Freespace observatory comes from an extension cord run through electrical conduit, which is placed inside the C-purlin closest the house. There is still plenty of room for the wheel to run in the purlin even with the electrical conduit in there. Basically, the shed needs to be plugged in, before use.

Nearly all of the telescope equipment and accessories that do not run on AC power, are powered by a single 12vdc, 11amp power supply. This DC supply powers the Skywalker, Dew heater, finder and guide reticle illuminators.

After several failed attempts to find the perfect flooring material for Freespace observatory, I came across this indoor/outdoor carpet. I don't know what it is made of but it feels like synthetic carpet, is rubber backed and guaranteed not to go moldy. . After removing the original carpet to put the outfoor stuff in, I found that it was significantly moldy underneath and very smelly after only 6 months.

As some know, I did have some problems with a neighbour during the construction of Freespace observatory. Because of this had to make inquiries into the legal requirements which need to be satisfied. Here is a short list of the points which make this particular observatory legal according to the Gold Coast City Council.

• A garden shed 3.0m x 3.0m or less requires no permit to erect
• Because no permit is required to erect the shed, it may be erected as you wish (i.e. with a roll-off roof)
• The shed may be placed on the property boundary if the following points are satisfied
• There is no window on the side facing the neighbour
• The shed is not made of combustible material
• The shed is more than 1.5m from the nearest neighbour bedroom
• The roof does not overhang the boundary

Of course any of these requirements may change over time and should be checked independantly.

A breakdown of all costs (Australian Dollars) that I can remember is listed. In total, the time taken to erect the shed and modify it was about 4 full days, taking into account that we did not really know what we were doing, and discounting completely the time taken to level and pave the area.