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Construction of Putlands Observatory (51º11'N 0º23E)



If you happen to speak Macedonian, you are in for a treat, these pages are translated here!
Putlands Observatory is a roll-off roof design and is owned by Crayford member Keith Rickard. It is based in semi-rural Paddock Wood in Kent (United Kingdom) where the visual limiting magnitude at this location is about 5.
The observatory houses a Meade 8" LX200 Classic schmidt-cassegrain telescope and can be remotely controlled from Keith's house. It received its first light on 9 October 2005. It is named Putlands Observatory after the area in Paddock Wood in which it resides.

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Keith Rickard owes a lot of the design of his observatory to Mark Baines and his Linnhe Observatory. The observatory is a metal shed and what makes the one selected particularly attractive is that its roof can be easily adapted to be a separate entity. A description of how he built it is given below.



A roll-off roof design was selected for the following reasons:
  • Cheaper than a dome (it cost £650, compared with a the cheapest offered by Telescope House of £2,750)
  • Quite easy to build - Keith has limited DIY skills and was able to build it!
  • Easier to see the sky
  • Cools quicker that a dome
  • It looks like a shed - important for security
  • Provides good protection from the wind

The most difficult and worrying parts were as follows:

  • Obtaining planning permission (not the council, but from the wife!)
  • Finding a pipe for the pier
  • Obtaining a pier plate (to allow the telescope mount to be fixed to the pier)
  • Getting rid off the soil (1 cubic metre of the stuff had to be excavated)
  • Laying the concrete (once laid - there was no going back!)
  • Building the wooden framework
  • The roof trolley
  • Getting started
All pictures are thumbnails - please click to view the picture full size. Click on your browser's 'Back' button to return to this page.
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This is the final product. The observatory received first light on 9 October 2005 at 01:00UT during its inaugural party of Crayford Members on 8 October 2005. Bits and pieces are still being done to it today.
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The observatory was sited near the house on a 6' x 6' footprint. This position did not to impose in the garden's aesthetics and maximised the southern horizon. The garden is SE facing meaning that good views are afforded in each direction except W and NW.
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View from the site looking South East
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View looking North
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He had great trouble trying to obtain a pipe for the pier. But one day while walking to the office, inside a skip outside a shop being converted by Tesco, was a 3 metre length of 10" diameter air duct pipe, used for air conditioning. It's amazing what you can get from Tesco these days!
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He then had to run inside his office, get permission and grab someone to help him take it and store it in the office. He received a lot of ribbing from his office colleagues, as you can probably imagine, but he didn't care!
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Getting this pipe then allowed him to get on with the build because without it, nothing could start. So he drove up the next day to his office (fortunately it was a Saturday - lighter traffic and no congestion charge), took the pipe outside and cut it into 2 an1 metre lengths and fixed the former length to the roof of his car.
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His office is in the City of London and it was amazing that he was not stopped by the police for driving around with what looks like a rocket launcher!
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The shed was bought from Argos for £179.99 and was delivered on 20 April 2005. A pdf file of the instructions can be found by clicking here. (You will need Adobe Reader to view it, which you can download from here)
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This is the box in which the shed came.
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This picture shows the contents of the box.
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Keith's father's friend was able to get him a 10" square 1/4" thick plate of steel. In fact he gave him two! The plates came from a step of industrial stairs that were being thrown out (the tread can be seen on one side). The spare plate will come in handy when (not if!) he upgrades his telescope.
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A plan was then drawn up. A concrete pad 6' x 6' and 4" deep was to be formed. A hole of about 3' deep was to be dug with a broken paving slab placed at the bottom for the pier pipe to be stood on. The slab would allow concrete to flow underneath the pipe. Four satellite corner holes also needed to be dug for 4 wooden corner posts to be concreted in.
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Digging began on 12 June 2005.
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A hole of the requisite size was dug in about 1.5 hours. The soil was mainly of clay and was fortunately easily to dig as there were no stones. A large hole filled with concrete will make the pier as solid and as adverse to vibration as possible. Concrete is excellent at dampening vibrations.
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Patio slabs were lifted so that a 6" deep trench was dug and two conduits to carry an armoured RCD protected 35A earthed power cable and computer data cables.
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CAT 5E cables and active USB 2.0 repeater cables were fed through 25mm white conduit tubes. A computer in the observatory can then be networked. Also, the telescope can be remotely controlled in the observatory or from the house along with any USB 1.1/2.0 device on the telescope (such as a CCD camera or webcam). The possibilities are endless - goodbye cold nights at the telescope!
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A 25mm hole was drilled through the wall of the house to allow the computer cables to pass through.
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Two 8 core CAT5E cables are from the pier and the other two are from the observatory corner. The USB 2.0 cable is from the pier via two active relay boosters.
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Two standard double network socket boxes are used.
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Preparation for the concrete pad was next. The base rails of the shed were laid out to identify where the corner post holes are to be dug.
putlands23t.jpg putlands24t.jpg putlands25t.jpg putlands26t.jpgPost-hole borers were used to dig 2 feet deep narrow holes for the corner posts.
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Shuttering was made to contain the concrete when poured. The inside was made octagonal so as to stop concrete from going down the post holes. The posts will be concreted in later, for good reason (explained below). Also, using the pier pipe off-cut, guide-lines were fixed to identify the centre of the pad.
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KERPLUNK!!The pier pipe was cut to the required length (so that the telescope can sit on it without fear of the rolling roof colliding with it). Side reinforcing and stabilising threaded rods were installed to fix the pipe securely in the hole.
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In the picture you can see how the pipe has been installed. The threaded rods had small plates fixed to them so that they could be forced into the wall of the hole to make the pipe as solid as possible. The pipe would not be able to be moved once the concrete is being poured.
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The inside of the pipe can be seen here with the reinforcing stablising rods in place.
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A plastic rubble bag was cut into strips and fixed to the shuttering to form a skirt. This will stop concrete from seeping underneath. The pad is now ready for pouring
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Next - work on the pier plate.Three 6mm holes were drilled through the plate and 8mm threads were tapped out so that three 8mm set screws could fix the telescope's wedge to the plate. Next four holes were drilled out for 12mm threaded steel rods (pier rods) to hang out under the plate in the correct position below. To ensure that these rods are set in precisely in the correct position in concrete, a framework was fashioned using two chipwood boards. The bottom board had a hole slightly smaller than the diameter of the pier pipe cut out and lugs fixed on its underside to fit it snugly on top of the pipe. Between it and the top board are spacers on each corner to allow concrete to be shovelled in by a hand using a trowel. The top board has the pier plate fixed on top with the pier rods hanging through it, ensuring that they will be in the correct position when the concrete sets. The pier rods are not reduced in length as they will also provide additional strengthening in the pier. At the end of each rod are two nuts cross threaded against each other to help stop the rods from ever turning in the concrete.
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The framework was then placed on top of the pier pipe on a clear night so that it can be aligned. A laser pointer (shown in pink in the picture) is placed flat against the wedge, tilted so that its beam is the same altitude as Polaris. The framework was then turned on top of the pier so that the beam pointed directly at Polaris.
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Once lined up with Polaris, the laser was laid flat, still against the wedge, and a mark was made on the fence where the laser beam shone. It was flipped over to make a mark on another fence down the garden.
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In the daylight, the framework could be re-aligned by pointing the laser at the marks made on the fences with the laser pointer flat against the wedge. During the concreting, this alignment can easily be checked. There is a 5º adjustment on the LX200 wedge still to get greater accuracy.
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So concreting commenced - no turning back now! Keith's friend Paul helped him here - a useful friend to know, especially as he owns a concrete mixer. Also, you can set him to work!
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1.2 cubic metres of ballast were ordered from the local builders merchant. 1.0 cubic metre was actually required but only bags of 0.6 were available. 8 cement bags were bought. A mix of one shovel of cement to four shovels of ballast was used.
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The pier pipe was filled with concrete first up to ground level. The hole was then filled along with some rubble to bulk it out up to ground level.
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Next the frame was placed on top and concrete was shovelled in through the gaps created by the spacers.
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Here, you can see the pier rods inside the pipe with the concrete filling up. No rubble was used in the pier to ensure maximum strength.
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The top of the pad was made smooth by gently shuddering a length of wood across the concrete and using a float.
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Here you can see that the pier has been filled to the top with concrete with the pier rods now in place.
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Job done! A week's wait is required for the concrete to set well enough before it could be walked on.
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This picture shows the pier rods now properly in place.
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The front right post hole is shown here along with the data cable conduit running into the pad at the bottom of the picture. The diagonal corners of the shuttering were removed.
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The shed base and walls are now erected. If the corner posts had been installed first then it would have been impossible to screw together the rear wall panels as they would have been too close to the fence to allow access.
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The corner posts could not have been accurately positioned until the shed had been assembled. Nor would they have been installed at the right depth so that the top of each of the four posts would have been level with each other. Details of how this was achieved is below.
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Done!
Keith said he felt a real sense of achievement on reaching this point as he now began to feel that he could actually finish building this thing!
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Each corner post was hung from a short piece of batten by a 100mm screw across each corner of the shed. This allowed the height of each post to be exactly determined by turning the screw with a screwdriver to raise or lower the post.
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The position of the post could also be finely adjusted and be made to enter the corner holes where required.
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The use of a 6 foot spirit level and tape measure ensured that each post was at the same height and correct distance as the others and vertical. All of the things are critical if the roof runners are perfectly level and parallel.
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Fast setting concrete was poured down each corner hole to secure each post. The post position was re-checked in the few minutes after before the concrete set.
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The wooden battens were left in position after the posts had been set in the pad so as to protect the shed in case of any possible high winds. It would otherwise be in a rather fragile state.
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The framework was then put together. It incorporates two long runners on which the roof will roll along. The wood used is known as "Superjoist" and is pressure treated. Each piece was given two coats of Ronseal wood preservative. The colour Forest Green was used as this match the colour of the shed nicely.
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The beams of wood are cut to length so that they sit snugly inside the shed. The picture here shows the corner detail. Each joint was held together with 100mm Screwfix Turbo Screws and wood glue.
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The runners had a slot cut through so that it could sit over the wall panels.
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The framework is set down below the top of the wall panels to allow them to be screwed to the frame.
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The runners were supported by a couple of long pieces of batten so that the location of the runner support posts can be identified.
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The post-hole borers were used to dig two 2 feet holes. The posts were fixed to the end of the runners with a 100mm screw and hung over their respective holes. A spirit level was laid on the runners to confirm horizontal accuracy. The battens were adjusted where necessary.
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Fast setting concrete was used to set the runner posts in place.Narrow strips of wood were fixed along the top of the wall panels to stop rain from coming in and protect the panel edges.
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Now work on the roof began. The roof ridge and gables were screwed together so that measurements could be taken to determine the size of the roof trolley.
putlands65t.jpg putlands66t.jpg putlands67t.jpg putlands68t.jpgWood was then cut to length, halving joints formed and the corners glued, clamped and screwed together.
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Eight castors, from Screwfix, were screwed to the underside of the trolley frame. Rubber tyred castors were chosen as they would be much quieter. Great care was taken so that all castors were perfectly in line and parallel to each other on each side of the trolley.
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The trolley is slightly wider than the shed so that weatherboards, which will be fixed to the sides of the trolley, have enough clearance with the sides of the shed. This meant that small blocks needed to be fixed to the inside of the trolley frame to allow the castors to run proper on the runners.
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The trolley was placed on the runners to determine where the guide rails. would be fixed
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The roof frame was placed on the trolley to ascertain whether it was going to fit properly. In the picture you can see the metal rails on the runners. These were 10mm right angled lengths of aluminium screwed on.
putlands73t.jpg putlands74t.jpg putlands75t.jpg putlands76t.jpgThe roof is locked very simply. A threaded rod engages with a metal strip (a Screwfix mending plate) as can be seen here.
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A simple door latch (cost less than £7 from Screwfix) is fixed as shown with the catch on the trolley. When the roof is rolled closed and the catch engages the roof is then entirely secure. All directions of travel are totally restricted.
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The roof is easily opened by turning the handle, sliding across the latch knob to lock the latch and then sliding open the roof. Adding or removing washers on the threaded rods can ensure that the trolley closes precisely.
putlands_film.gifputlands79t.jpgputlands_film.gif putlands_film.gifputlands80t.jpgputlands_film.gif putlands_film.gifputlands81t.jpgputlands_film.gifClick on one of these pictures to watch an WMV video of the locking mechanism in action.
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Weather boards are fixed to the back and front of the trolley. The roof is now ready to be built. By placing the trolley on the garden lawn makes it easy to do this.
putlands83t.jpg putlands84t.jpg putlands87t.jpg putlands88t.jpg putlands89t.jpg putlands901t.jpgAfter the roof panels were fixed to the roof frame a strip of flashing tape is stuck along the top before the ridge cover is screwed on.
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Rubber draught excluder strips are fixed to the left-side weatherboard to make a seal with the roof when it is closed.
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The right-side detail can be seen here.
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The right weatherboard has a section cut out of it to take account of the rail and runners.
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The remaining concreting is completed for each corner. The concrete is mixed by hand.
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Two bulk head lights, one white and one red, were installed. A dimmer switch, which is turned to switch the lights on and off, was installed. Using this kind of switch would mean that when switched on, the light starts dimmed and so saving your retinas from being burnt out!
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A two way switch (double pole, single throw) was also installed so that the white or red light, not both, could be selected. 60 watt bulbs which provide sufficient light in the observatory.
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The inside of the glass lens of the red light was sprayed with a cheap red craft spray paint (this cost about 70p). About three coats were made.
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This picture shows the effect of the red light. Red light is used when observing as it is far less destructive to an observer's dark-adapted vision compared to other coloured light.
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A utility shelf was made from a piece of MDF board was cut and shaped, with 12mm holes cut so that it will sit over the pier rods.
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B&Q were throwing out Disney's Buzz Light Year Warp Speed Blue paint for 75p per tin! It is an ideal colour for the inner walls of the observatory as it is dark and reduces the scattering of light. In this picture, the pier, being galvanised steel, was painted with Hammerite Special Metals Primer.
putlands912t.jpg putlands913t.jpg putlands914t.jpg putlands915t.jpgThe pier was painted in black Hammerite paint. Strips of batten, painted with wood preservative paint, were placed on the concrete pad so that tongue and groove loft floor boards could be laid on top. These battens would protect the boards form any water ingress. A carpet was later laid which provides insulation for feet and protection from dropped eyepieces, etc.
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In order to save space on the pier and the corner, network cable connectors were glued together and screwed to a small piece of MDF. This provide a good alternative to using network socket boxes.
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The electrics in the corner contain 2 metal clad double sockets, a 60 watt tube heater (to reduce condensation), 6 network connectors and USB 2.0 cable for connecting an observatory computer to one in the house or a device at the telescope, and a 12v power pack to provide power at the pier.
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The telescope was at last installed on 6 October 2005. This picture shows that moment. The telescope was perched very high on the pier rods and was later lowered to increase stability.
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In this picture with the telescope properly installed. Near the bottom is a mini grey gang plank which provides 12v DC via cigarette lighter sockets provided by the 12v power pack seen in the picture above.
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Azimuth adjustment to the wedge is provided by having two 8mm bolts with two nuts set into the pier plate. A cheap 3" G-cramp is then used to pull the T-piece fixed to the wedge towards one of the bolts as necessary. The bottom of the wedge has been lightly greased to facilitate this.
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Once the azimuth adjustment has been made, the set screws which fix the wedge to the pier plate are tightened. This picture shows how well the pier plate and rods were aligned with north. You can see that the edge of the wedge deviates very slightly with the plate edge. Very satisfactory!
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The latitude adjustment is made by using the wedge's own adjuster. The two side knobs are released on the wedge tilt plate first, the latitude adjustment knob (bottom right of the picture) is turned so that the tilt plate moves in latitude angle. Once set, the side knobs are retightened.
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The original shuttering around the concrete pad was painted to finish off the observatory. Security has been provide with a padlocked door, security screws in strategic places and an alarm system.
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The main problem with metal sheds is condensation forming on the inside, especially on the ceiling. To solve this some polystyrene ceiling tiles were bought, the reverse of them painted with emulsion paint and then carpet glue spray was to stick them to the ceiling (the emulsion paint stops the glue from melting them) - thanks to Julian Tworek for this tip. Perfect!
putlands_film.gifputlands924t.jpgputlands_film.gif Click on this picture to see an animation of the roof opening (wmv file 473K).
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With the observatory now complete and operational, Keith can now be up and running within minutes. Observing has become much more frequent and pleasurable. Keith says that it has been the best investment to his hobby after his telescope and the best project that he has ever undertaken. He would recommend it to anyone.



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CMHASD - PutlandsObservatory