Observatory in Kirkintilloch

[LongJohn54]

I retired in 2014 and decided it was a good time to build an observatory.  Not having to get up for work meant that late nights were no longer an issue.  I intended to write a build thread as I worked but as the build progressed very slowly I decided to wait till it was complete.   Progress got underway in April 2015 and the obsy was completed in October 2016. I took photos of everything and made notes as I went along.  During the build the local streetlights were all replaced with LED lights.  Fortunately this has improved the overall light pollution.  I have now culled 700 odd photos down to a more sensible 175, so here are the photos with notes made at the time.   It might take a while to get it all posted...

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I live half way down a hill, surrounded by houses and streetlights.  Four streetlights overlook the garden with another eight beyond the house but within 150 metres.  There are plenty of trees to the southwest and northwest too.  An observatory will give me a dark space out of eyesight of all the lights and neighbours windows plus a permanent base will save so much time setting up. 

Over the last six years I’ve read pretty much every build thread here.  My favourite is Aoraki’s build http:// https://stargazerslounge.com/topic/119083-aorakis-build/ which scores highly in style and build quality as well as function.  I would copy it but don’t quite have enough space.  Next is Malcolm’s build, https://stargazerslounge.com/topic/100997-observatory-build-underway/ followed by many other similar builds.    I’ll be taking ideas from all of them.  The basic design will be a 2 metre square obsy with a 2 x 1 metre warm room.  The warm room roof will be fixed and the rest will roll off northwards.  I did consider putting the warm room to the north but this puts the pier too close to the garden border restricting my southern view.

I should also mention yesyes and Gina for their comprehensive design and build threads.  If I can get half as good I’ll be happy, also thanks to Gary1968 and Lorne for their contributions to the build.

Google Earth view of the garden and where the Obsy will be sited.  I’ve no storage space so I’ll get materials when I need them.  ‘Just in time’ or as it often turned out ‘Just before it rains again’.  There is no access to the garden except through the house so everything has to be brought through the front door, hall, dining room and kitchen and out the back door.  It’s going to be fun!

The garden with my normal setup.  I put a length of hosepipe around it on the ground and sat in my seat checking my views with the scope at all angles and whether I had enough room to manoeuvre.  I decided I could just work within a 1 metre radius.  It would be tight though.  (All those shrubs beyond the fence are much taller now so the houses are hidden and my southern view even more restricted.

Proposed size and location with the brick representing a pier.  Looking at it I now think it needs to be a bit wider.

 

[LongJohn54]

Scope looking at the southern horizon (it’s uphill all the way!)

Scope looking at the eastern horizon over our house

Scope looking at west over neighbouring roof

Scope looking north (now that’s a horizon!)

 

[LongJohn54]

My view Northeast

My view East

My view Southeast

My view Southwest

My view West

The view Northwest is blocked by trees.  Overall the view is quite restricted but there’s still enough to justify building an obsy.

[LongJohn54]

Outline plan to be approved by the boss.  She approved, Yaay!

The foundations arrive.  They are aerated cement Handiblocks with a fibrous filling that can support 850Kg each on a footprint of 30cm square.  I’ve got 10 which should be plenty. 

Lifting a slab revealed 10mm of sand on top of compacted soil.  I removed 150mm and found firm subsoil which I think should be ok as a base.

Added 50mm of sharp sand and compacted it very firmly and level.

The first block is in and level.  Yeeha!

[LongJohn54]

Added a second one and ensured it was level. 

Placed one inbetween.

This block is 14 inches lower than the others.

The joist will be supported by a post of some sort.

The joists arrive.  They are pressure treated and guaranteed 15 years for ground contact. They won’t touch the ground though.

[LongJohn54]

The Handiblocks are cast with 47mm slots, the joists are proper 6 x 2’s so 51mm thick. Something needs to be done.

A Tenon saw makes short work of resizing the slots and surprisingly the saw isn’t damaged or blunted by the block.

They now fit.

The width is finalised at 2.2 metres.  The extra 20cm room will be useful.

[LongJohn54]

The joists are joined on the outside with 100mm screws

Joined with right angle brackets inside.

I made support posts for this end from offcuts of joist fixed with plates on the outside and brackets inside.

I treated all the cut ends with Ronseal Total Woodcare then painted the whole lot with it just to give an even finish.

A square is formed with string and the remaining area will become the warm room (now 80cm wide rather than the 100cm planned).  I‘ve added the warm room joists.  I’ll remove the paving slabs as and when I need to.

[LongJohn54]

X marks the spot.   Seems like a good place for a hole.  It’ll be 70cm square and 80cm deep.  Rebar will be hammered in another 60cm as well.   The original design was for a concrete slab 100cm square and 20cm thick.  A brick pier would be built onto it.  However the boss liked Malc_C’s pier and that soon became the preferred design.

Malcom’s pier.  As the boss says – too good to exist in only one observatory.

George from next door popped round and between us we dug this out in a couple of hours.  I’ll expand and tidy it up so it’s the same size as the frame.  The string was removed for the dig and replaced for the photo.

I used some Contiboard to give a clean edge to the top of the hole.   I made a frame to locate the bottom of the pier centrally.  The 3 inch nails into the subsoil hold this in place.

I bought a 3 metre length of 200mm pipe from Plastics-express.co.uk and cut it to length (one of the few calculations that had to be accurate as I want to observe as well as image).  It’s located firmly by the upper and lower frames.

[LongJohn54]

Two 1 metre lengths of 10mm threaded rod were cut in half and then one end bent.  It’s tough stuff.  I had to lean with all my weight to bend it.

I made a jig to hold the rods in place.

As seen from inside.

Rebar was hammered into the ground around the pier and three pieces inside it.   The bottom of the rebar almost touches the inside edge of the tube.  Halfway up it is bent inwards to form a pyramid.  There is enough space for the threaded rods to fit around it.

 

[LongJohn54]

I bought a washer.   It’s 274mm in diameter with a 14mm hole.  Its 5mm thick too!  I got it from Lasermaster who will laser cut any size washer you require.

The washer will fit between a couple of Laguna brake disks.  My mount sits nicely on top of one.  I went with brake disks in the end due to not getting a machine shop to copy Malcolm’s pier top for a sensible amount of cash.  £140+ for a bit of turned aluminium, madness!

Despite the website photos showing no external bevel these disks do have a very deep one.  This is a tad irritating as the mount now has 3.6mm free play whereas I was expecting 0.2mm.   One of my observing buddies (Gary1968 on SGL) kindly drilled holes to my specification and painted them for me. Thanks again.  These three items weigh 16Kg, the same as an EQ6.

 

[LongJohn54]

 

 

Another observing buddy (Lorne on SGL) supplied the 16mm threaded rods and nuts and washers.   Thanks again.  The disks are placed into position and the mount was added.  Just got to wait for nightfall.

That tree does not quite obscure Polaris.

The template upended.  As planned the rods fit neatly around the pier rebar.

The morning after the night before!  I’m lined up with Polaris and marks were made on the template and pier to ensure I can match this position again.  I’m happy to go ahead with concreting.

[LongJohn54]

I had wondered how to mix the concrete and was dreading the traditional hand mix with a spade.   Luckily Yesyes had shown the way forward with a drill and paint mixer so I bought a screed mixer which is much more heavy duty.  It is normally used with a 2Kw motor so how will my 750W Mac cope with it?

No bother at all really.  According to the internet a good water to cement ratio by weight is 40% with a maximum of 55% before the concrete loses strength.   I started by weighing 5Kg of cement into a bucket then I marked the fill level in the bucket for repeatability.   As for water, I filled a 2 litre (2Kg) plastic drink bottle.   The ballast comes in 25Kg bags which were pretty damp from sitting in the garden being rained on for a few weeks.  So I'd end up with a 5:1 mix plus 2Kg of water making 32Kg of concrete.

The process was to pour 1.5 litres of water into the bucket and add the 5 Kg of cement.   Give it a wizz with the drill until it was thoroughly mixed into a wet paste then add the 25Kg of ballast.   Mix and add the remaining water.  The fact that the ballast was damp meant the mix was nearer 41% than the ideal.

As long as I stood upright mixing was easy.  I could have done that all day.   The 750W drill was set to the slowest speed (too fast made a hole in the middle and didn't mix anything).   Lifting the bag of ballast and pouring it into the bucket was much harder than I thought it would be.
Walking to the garden tap to refill the bottle was good to relax the muscles between mixes.

Working next to the hole meant little lifting; I just heaved the bucket over and poured it into the hole.  Well, I say pour.  Whilst the mix was wet and evenly mixed it was stiffer than the readymix you get delivered.  The bucket needed a good shake and scrape to get the concrete out.   I set the drill to vibrate only mode and pushed it into the concrete.  A 10 second buzz settled and levelled it.  Amazing!  Just repeat 28 times.

To fill the pier I scooped concrete from the bucket into a plant pot and poured that in.  After each pot the mix would be tamped down with a stick working around the rebar.  I wanted no air pockets.

Once the pier was almost full (2mm from the top) I pushed in the rods and positioned them against the marks I made when aligning previously.  Very satisfying!  I expected this to bring the concrete to the brim.

The top view.  The pier was covered with a bin bag while it set.

A few days later I removed the jig.  The concrete now 3mm from the top.   I’ll add a finishing coat of cement to bring it to the brim though.

 

[LongJohn54]

Cutting the joist hangers for the middle of the base.   I bought this workbench in 1973 (I think) at an Ideal Home Exhibition.  The slots are to hold a single ended vice and the holes will accept the other end.  In this way you can clamp anything from 5mm to 1000mm wide and it will support a door easily.  It will clamp a right angled joint too which has been useful.   Just hidden is a cut out to accept a circular saw as well.  It was clearly better than the flimsy looking Black and Decker Workmate that was at the same show.  That’ll never catch on I thought (Ha Ha!).

Warm room floor insulation.  50mm insulation sitting on plywood resting on battens screwed to the joists.  Before putting the floor down I painted the battens and ply.

Flexible tube for cables.  Two just in case!  Also prethreaded with drawstring.  Having now finished I’ll mention at this point that this was a poor idea.  The tube has a lot of stiction making it really hard to pull plastic cable through it. Rigid waste water pipe would have been better.

The pier top filled to the brim.

[LongJohn54]

Take three sheets of OSB3 and cut to fit.   I painted these with two coats per face and four coats per edge with Ronseal Total wood preserver before fitting.

Floor fitted.  Yes, it has rained.

In fact it rained and rained and rained and rained some more.  It was pretty windy too.

Just had to check if things were as they should be.

Looks good to me.

 

[LongJohn54]

Mark and cut the top and bottom of frames.  All square so far!

Making the back frame.

Frame wood cut and stacked

Storm expected.  Seemed to have quite a few this year.

 

[LongJohn54]

 

Frames levelled and square.  Looking good so far.  That’s me with the grin.  The floor is wet and will remain wet for a couple of months.  I’ve removed the bin bag from the pier as it never stays in place.   The bucket on the pier just works!

The forecast was cloudy but dry.  No rain. No sleet.  Absolutely NO snow.

Diagonal bracing being added. I marked the outside frame edges so I could reposition them in exactly the same place as I will be cladding one frame at a time.

There will be stone chippings around the side and back for weed prevention and to look good.  Overnight the temp fell to -9c.  The bags of stone chippings are frozen to each other and the floor.  The floor is an ice sheet.   How and why does it get and stay wet under a tarp?  I worry about the floor.

 

[LongJohn54]

I stapled vapour barrier to the frame and took care to align the first length of cladding.

There is a 50mm overhang to cover the edge of the floor.

There will be no room between the fence and the Obsy so the back wall has to be fully finished before fitting.  Here it is temporarily fixed for assembly.

Various lengths of wood and several bricks support one end while I work on the other.

Notice how the snow is settling more on the warm room floor.  The insulation appears to work.

 

[LongJohn54]

It’s green!  Three coats of Two Coat Fencelife.

With the paint fully dry I now have to unscrew the temporary fixings and walk the wall backwards into place.  George pops round again and together with Maureen (the boss) we get this done.  It’s very heavy and unwieldy.

The other three frames are positioned and once everything is level and square the back wall is screwed through the floor into the joist with 100mm screws.

The end wall also has to be partially clad before fixing as well.

[LongJohn54]

Cladding drying in the sun before cutting and fixing.  Did I mention that it rains a lot up here?

The end wall is fitted and lined up square.

With the other frames added and aligned all frames are screwed down and to each other.  Vapour barrier is then stapled all around.

A temporary roof of clear plastic is attached.  It rests on a pack of cladding plus loose pieces of waste cladding.  This allows daylight inside so I can work and see what I’m doing.  All the wood is moved inside away from the weather.  The floor is still wet though.  Overnight a proper tarp is pulled over the whole thing.

 

[LongJohn54]

The cut out for the door frame.

The first board is fitted exactly the same height as the back wall.  The cladding should be level all around.

It’s coming along nicely.  While I’m hammering away some of the cross pieces supporting the clear roof cover fall down.   I remove them all.  What could go wrong?

One short and heavy downpour later and with no support the plastic filled up.  Good job it held and didn’t tear.  I scooped out the water with a bucket and replaced the supports.

Despite being careful with fitting the cladding didn’t match up exactly.  The cladding varied between 118 and 119mm in width leaving me 12mm short at the top of this wall.

The doorframe installed.   It’s untreated so had a coat of paint before fitting.

 

[LongJohn54]

I’m making the door out of two sheets of ply sandwiching a simple frame.  I bought an offcut of glass and drew around it to make the cutting line for a window.

The frame is glued to the ply.

The window frame and cross piece with bubble wrap for insulation.

and the back glued in place.

Fitting the hinges and trial hanging the door.

 

[LongJohn54]

Some minor trimming required to get a good fit.

Primer-undercoated.

Drilling out for the door lock.  It’s an insurance approved 5 lever deadlock.

The door fitted. With the door closed I fitted the door stop all around the frame using a credit card to give me a 0.5mm gap.  By the time everything is painted there will be no gap and the door will be tight against the stops.

All wrapped up again.

 

[LongJohn54]

Woo! 8 kilos of brass!  They are load rated at 140Kg each. 

Glued, screwed and bolted.

The roof rollers on the side frames.

Levelling the first rolling roof runner and fixing a temporary support.

The 3x2 roof runners with temporary supports.  I’ll add steel angle to support them.  This will give a much lighter construction than the 4x4 timber needed for the maximum potential weight (roof plus half ton of snow).  Not that it’ll be opened with snow on it.

 

[LongJohn54]

Wood for the rolling and fixed roof resting on the half built warm room wall.  Yes, the floor is wet.  I was going to paint all the exposed framework of the roof with black bitumen paint but having started I discovered it never fully dries leading to black fingers when handling it.

Two or three cladding boards for the rolling section?  Three gives a stronger triangle plus the roof will shed water easier with the increased slope.

The wheels clattered over the joints between tracks.  10mm threaded rod fitted in the gap plus filing the ends carefully has made a smooth and silent join. Perfect when shutting up at 3am!

Rolling Roof construction.

Rolling Roof construction.

Rolling Roof construction.

[LongJohn54]

Drilling holes in steel angle.   Measure, scribe, centre spot, drill and countersink.

Fitting an end post underneath the steel.

The view from below.  The steel angle strengthens the runners so that I can suspend myself from them without them bending.

Bracing timbers. Manoeuvring and aligning three pieces of timber single handed can be challenging.  However, quick release clamps really help.