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A Fenland Observatory


JohnC64

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Well after many years of saying - “I really need an Observatory”  I have finally found some time to get my plans under way.  I could have equally have called this thread “The Plagiarised Observatory”  as I have read virtually  every thread in this section over the past few years and have  blatantly stolen many of the ideas previous published in many other threads.  In no particular order many thanks to SGL members Tinker1947, Malc-C, Bizybuilder, Gina, and YesYes for their generosity in publishing the information that has been so useful to me.
 
One advantage of living out in the Fens is that we get very good dark skies. The disadvantage, for this project, is that the ground is  very mobile.  My garden shed is moving inexorably to the North east all by itself!!.  (you can just see at the roof sag in  pic 1 !!!)  To this end, I have had to dig all the way down to reach the clay gault, in order to reach some stable land mass on which to build the observatory. ( about 14" at the deepest)
 
The site is at the north end of my garden and gives me the best southern view combined with the security of the location.  The first task was to move the logs stored from an old willow tree that was taken down last year.  The land isn't level at this point and slopes down towards the NE direction.  In order to dig out the required depth, I hired a Mini-digger for the Bank holiday week end.  After a quick practise in the paddock digging my ditches out and then went for it. With about 7 axis of movement it is very much a mental challenge to co-ordinate all the levers but very rewarding when you get it right:-)
 
Warning - I will be mixing imperial and metric measurements with little regard to the reader’s sensibilities. ;-)  I still think in imperial but have adapted to the metric world when required :-) 
 
I am looking at  building a 12’x8’ roll off roof observatory  (2.4mx3.6m in new money)  comprising an 8’x8’ square obsy area and a 4’x8’ warm room to the north. The Roof will roll off to the North.  On the South side, I am looking at a hinged wall so that I can fold the top part of the wall out of the way to give me better views.  The corner posts will be a 4”x4” with a 4”x2” top rail on which to mount the track and runners.  I am going for the FH Brundles V-Track with 4x 80mm internal wheels on each side.  I could have probably got away with 3 each side, but as the ROR is the most important aspect of this build, I decided to add an extra set just to over engineer a bit.
 
After digging out the basic plot, I added some shuttering to give me the basic outline and also installed some shuttering for the central pier block 80cm x 60cm x  80cm.(WxLxD)  The shuttering will not win any wood-working awards as its a bit “agricultural”  but its square and level which is the main thing.

I have also added some ducting(left over from when the Garage was built) to link the central pier area and the warm room.  I will initially power the obsy from an extension lead from the house from an outside socket to an outside socket on the side of the building.  In anticipation of having power supplied direct from the house, I have also provided ducting to allow this at a later time. At present though this external ducting will be blocked off.

 
The aggregate arrived today and with the help of a friendly local farmer had it brought through the paddock and lifted over the fence much to the surprise of the sheep :-). It was positioned just a couple of meters away from its final destination and this saved a massive amount of work.  I also have the sand in the same place, ready for the concreting phase.
 
Also today the outside cladding arrived, (now safely moved into the garage). I have gone for 28mm log lap to be fitted over a constructed frame. It will follow a similar building technique that buzibuilder used here http://stargazerslounge.com/topic/187362-bizibilders-new-roll-off-roof-observatory-build/page-4?hl=%20willow%20%20green I will also be using the willow green colour for my observatory as it will match the existing fence panelling around the  patio :-)

I have now filled the ‘hole in the ground’  with 5 builders sacks of granite hardcore and will finish that off tomorrow when I pick up a plate compactor and the cement mixer for the next phase.  I will post a photo tomorrow of this stage as the heavens opened and had to get the tarp over to keep everything dry.
 
Here are the photos of the various stages so far.
 
Cheers John

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A man with a faithful dog, gloves on his hands and dirt on his jeans spells success in my book any day! It's that attitude of quiet determination that makes all the difference and there's just no substitute for creating something you've been dreaming of for years with your own two hands.

I can already tell your new observatory will be a great success & I look forward to your future updates as I'm smack in the middle of a DIY - one-man build - as well...  :icon_salut:

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Hi All - many thanks for the words of encouragement.

As promised yesterday, here are some pictures of the site with the hardcore filled in and also of a couple of bits of hooped rebar down the pier section.

The  plate compactor arrives tomorrow with the cement mixer for pouring the pier section.  It remains to be seen if I need another bag of Granite hardcore to top up if It sinks down too far after compacting.

Cheers John

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Its been a busy couple of days over the weekend. I have now removed the excavated soil and  also have the pier concrete block poured. I am waiting for that to fully harden before removing the shuttering.  When I pour the outer concrete block ( probably Wednesday) I was going to isolate it from the pier block  with sheets of Selotex   thermal insolation cut to size.  It is about 65mm thick and i can trim it exactly to size when the second pour has hardened.   Has anyone done this before?  I have seen various materials used (Yoga mat, polystyrene beads, 10mm gravel etc ) but haven't seen selotex board used.  So the selotex becomes the shuttering and the dampening isolation.

What do people think - Good idea or not??

I have also started buying bits for the pier and have managed to get a EQ6 pier adapter from JTW in Holland..  They are selling them a lot cheaper than other ones I have seen - About £32

It appeared on Amazon as a You may be interested in item.... (its scary what Amazon knows :-) )

http://www.amazon.co.uk/Skywatcher-EQ6-Mount-Pier-Adapter/dp/B00ZMDGTDC

There also appears to be a youtube video of them being made on a CNC machine  here

The wood for making the framework for the walls should be arriving tomorrow, Along with a trip to screw fix :-)

Cheers John

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Cheers Tinker - Yes its a firm foam board (Celotex  is the correct spelling) used for thermal insolation.  I have half a dozen boards left in the shed and was going to use it to insulate the warm room. but have more than enough to use it as spacer.   http://www.insulationshop.co/65mm_celotex_ga4000_pir_insulation.html

Thanks John

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Hi John,

Nice project and location! 

I looked at Celotex when I was thinking about pier insulation. If it's the same stuff that we had put under our floor, it's a polystyrene-type material faced with some aluminised foil; ours was quite thick  - maybe 10 cm or so, but easy to cut with a knife.  I found it was quite a rigid material and rather than having a spongy, compliant behaviour, the bit I tried resisted compression until it deformed permanently (similar to the "oasis" stuff people use for flower arranging, but more pressure needed to deform it). So I thought it might not be the best choice for damping the transmission of vibration from the floor (though it's undoubtedly a good thermal insulator!)

I've currently got a small air gap around my pier, but I decided that foam water pipe insulation was possibly  a better choice - it's more spongy so should help to attenuate any disturbance coming from the surrounding floor.

Just my 2p.

Hope things continue to go well.

Cheers

Nigel

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Hi Nigel,

Thanks for the input.  I had a play with  the celotex board that I have today and have found that it does have some give and then restores.  If I really stress it, it permanently  distorts as you describe.  I'm not expecting that much movement between the pier block and the  so I don't think that it will be a problem . As it is of a 'honeycomb'  construction, the sealed cell structure should be good in preventing damp too.

I will give it a go and see how I get on.  As you say, it is easy to work and if it doesn't prove to be successful, I will be able to remove it easily enough

Many thanks for the feedback

Cheers John

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Well that was a hard day yesterday.  I now have the concreting finished, at about 9pm last night having filled the outside framework with nearly 4 tones of sand, aggregate and cement. Which probably explains why I am a bit achy today :-)

I may need to run over the top with some levelling compound to get a smooth finish but will be having flooring in the warm room and grey rubber matting in the  obsy so may get away with it

Here are some pictures of the 'finished'  base.   I  will trim the celotex  back in a day when everything has a chance to firm up.  Now I will start to build the stud work for the walls.

Cheers John

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Also today I have had the Pier adapter arrived so I need to get that over to a small local engineering firm who are building my pier for me.  I will be chem-bolting the pier down using something like this http://www.sealantsonline.co.uk/ProductGrp/001c0001They only go upto M12 though and I'm not sure that that will be big enough (probably thinking M16 would be more like it)

What is the consensus on the bolt size to use for bolting a pier down?

Here are some pics of the pier adapter

Cheers John

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  • 2 weeks later...

Hi All

I've made some progress on building the framework. I am back at work now so progress is a lot slower.  The external stud work frames are now built and  I am staging the build in the garage to get any wrinkles out of the way.  The 4x4 corner posts are now drilled so that the stud work can be coach bolted together.  Tomorrow tasks will be to finish the internal wall, and connect the small part of the frame onto the frame with hinges.

Heres a photo of the build so far.

Cheers John

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Hi John - Your build is looking good!

That framework looks heavy so I'll ask the obvious question - how are you planning to get it out to the pad or are you going to disassemble it and put it back together again?

Might want to consider something more substantial on the top two sides where the tracks will be mounted. Those look like 2×3's but wonder if 4×4's (like on the corners) might be stronger and wouldn't move as much keeping the tracks in alignment & on the same horizontal plane.

Just a thought but you'll probably be fine...

Looking forward to your next update :)

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Looking good. +1 for a more substantial running frame at the top. I would also make sure you really treat the wood very well with a wood preserver. If possible two coats,( it soaks in and often requires a second). I would make sure you separate the wood from the concrete with a damp proof layer and make sure the outer shed skin hangs over the outer edge of the concrete base with damp proofing between it and the concrete. Finally I would dig back the soil and grass from the concrete edge so it is about 4 to 6 inches lower than the concrete and top with gravel, for about 12/18 inches width around the outside.

You have put in a lot of work and more to follow so good luck with the rest of the build.

Derek

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Hi,

And another +1 for substantial from me too :-).

I have 4x2's ready for attaching to the top to which the tracks are to be attached and the running rails for the roof are also 4x2's.  The roof joists will be 3x2's.  All the wood is pressure treated with Tanilith  and kiln dried so hopefully will be good for a long time.  Hi Derek - You have described almost exactly what I am going to do.  Also I will be adding guttering and putting in a drain to a nearby ditch to allow Rainwater to escape.  I have damp-proof membrane for under the wooden framework and also breathable membrane to go under the  log lap to form a barrier.  Hopefully this should keep the elements out.  At the moment everything is held together with screws so that I can dismantle and move/ reassemble and fit the coach bolts.  The next major task will be to do is build the rolling roof

Tinker & Alex - you were spot on about the M12 bolts I now have the M12 chembolts and they look very substantial :-)

Many thanks all.

John

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Sounds a great project. I will await your next reports. It is something I am desperate to do myself when I have finally moved house. There are so many good builds documented here on SGL, so loads of ideas and good information to be had.

Best of luck,

Derek

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  • 2 weeks later...

Hi all,

I've managed to have a very productive couple of days and have moved the observatory on quite a bit.  The framework in the garage was dismantled and moved onto the pad.  I have put a layer of  damp-proof plastic on the bottom under the framework to prevent any damp coming up.  The frame is now securely bolted together properly with M12 coach bolts . 

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The next task was to wrap the obey in breathable membrane and staple it in place.  

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I have also fitted the top rails to the top of the framework to complete the base structure.  I still need to create concrete pads for the support post to go on  sitting on  a stand off.

The next job was to fit the log lap to the frame.  Measuring this at the start of  project paid off as I managed to reduce the cutting of the boards to a minimum and completed the base structure far quicker than i expected.  I still have  one piece to fit around the join of the drop down window. so that the hinges open/close properly.

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The final task was to give everything a couple of coats of Cuprinol Willow shade  and when it dried get a tarpaulin over the top for the evening

The  next task on the agenda is to get the roof built and fitted.  

Cheers John

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Looking very nice indeed.

Question: are you planning to cover the corners of the observatory? I see the end grain of the cladding is exposed in your photos, as it is in my build. I understand this is one of the areas it's important to protect because moisture wicks up the grain, so I was planning on tacking and sealing a thin, narrow strip of wood mounted vertically on each side, at every corner.

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