Thoughts on Small Garden Observatory

[jACK101]

I am thinking about building a small obsy in my back garden. I have trawled through quite a number of previous posts on this topic and have gleaned a number of ideas which I would like to incorporate and some that I definitely don't want to incorporate e.g. the instance when the roof blew off is something I will try to avoid.

I have checked with my local planning department and I do not need planning permission for what I have in mind. I would welcome any points that anyone cares to make to ensure that I am moving in the right direction and avoiding potential problems.

What I have in mind is the following:

 

A building of roughly 2m *2.5m. It should be large enough to accommodate 3 people at times, plus chairs/stools  and a small desk or work surface.

Concrete footings for a single run of bricks. Footings or 2" thick concrete over entire floor surface  to support chipboard floor which will be laid on a waterproof membrane. Screwed rod to be fitted to footings as they are laid and providing anchorage for 3 x 2 plate on top of bricks.

Stud partition walls with exterior plywood (or other suitable material ) cladding, height internally 6' (I am 6' in height) I want to keep the profile of the structure as low as possible to minimise wind loading but also to minimise visual impact. Finished structure will be painted in darkish colour.

Roof, with reference to the example where the roof blew off, I did originally plan to make it as light as possible to make it easier to move, but I think a heavier structure might be safer. Therefore a timber, probably 3" x 2" frame with corrugated steel surface. This will have to be insulated to minimise condensation.

A track on either side for roof castors to run in. The roof will only need to roll about 1m to allow access to the area of sky I plan to use. The corrugated steel will extend 6" beyond the walls to minimise water ingress.

The obsy will face due South and will have an available horizon from South round to East. There are trees very close on the West side which makes a Westerly view almost impossible, but does have the benefit of providing quite good protection from the prevailing winds.

I will still have the use of my Celestron tripod to use the scope away from home.

The top section of the Southerly wall will hinge down to allow the use of the scope. The South Eastern top section of the wall will hinge backwards to allow access to Eastern sky. I will probably leave the South Eastern  corner stud supporting the walls and roof in place and just accept that it will slightly impede my view at times.

The roof will be operated by a manual trailer winch which will be anchored to the back wall. Stops will be fitted to the track to stop overshoot of the roof. The roof structure will also incorporate   a timber structure to keep it "captured" so that is another precaution against blow off.

When obsy not in use the roof will be tied down at the 4 corners using either toggle clamps or rope tied to cleats.

 

I also intend to build a pier to carry my Celestron CPC925.

This will be conventional concrete construction, as large as I can manage. The soil is sandy and drains readily. I like the idea I have read about in another post for using car brake discs as a top plate and I will investigate that. My original idea when I started taking an interest in Astronomy was to get into Astro photography. I have been a keen amateur photographer all my life. Looking at the equipment required to get the best results is putting me off this idea and I think I will concentrate on using my DSLR a NikonD3200 to its limit first of all.

This raises an issue which has an impact on the design of the pier. i.e. Do I need a wedge? I need to decide that early on because it will have an impact on the height of the pier. Bearing in mind that I am trying to keep the overall height as low as possible, this could prove embarrassing if I can't get the pier assembly into the overall height of the structure.

The Celestron wedge is quite expensive and I wonder if I am using this from 1 location only do I need an adjustable wedge or could I get someone to weld up a structure designed for my latitude? Would this work out cheaper and would it be effective?

I plan to shutter the concrete of the pier and embed screwed rod to accept whatever top Plate I end up using. I would then clad the exposed part of the pier within the building in an attractive timber.

There will be no windows in this structure and the door will be as strong as I can make it, therefore it will not be immediately obvious that there is expensive equipment inside. Is it best to rely on anonymity or to put a visible alarm outside which then broadcasts that there is something valuable hidden in there.? Also the height of the building will make it impossible to put any alarm out of easy reach.

 

Thank you if you have had the patience to reach this point, and I welcome any comments that anyone may want to make. I feel it is best to get as many issues sorted out before starting on such a project.

 

I will keep you posted, but progress will be very slow due to my current health.

 

Jack

 

 

 

[Daz69]

Hi there Jack.

I don't wish to rip your idea apart, but if I was building as obsy, and I wanted it to be right first time, I'd go with something like this:

In regards to a concrete floor, 2" isn't really thick enough, and any movement of the soil underneath will cause it to crack, even with anchors. Suggest minimum 4" thick laid over scalpings. My 20'x10' wooden framed workshop sits on 5" thick poured concrete, and that hasn't cracked or shifted. No need for reinforcement or anchor bars unless your ground is steeply sloped or likely to subside, but I'd lay the WPM under the concrete to stop damp rising through it, which will be even more better. Above this, lay some 2" thick polystyrene sheets for insulation, as bare concrete, even with board on top, will cause your legs to fatigue (I've spent too many years in my workshop to know this!). Space out 2x2 battens and screw to concrete, then put the styrene in between the battens. Then lay your boards onto the battens.

If you go with the corrugated sheet roof, I'd have a breath space between that and a solid board roof underneath that is also insulated. That should help with the condensation issue. A heavy roof is easily moved if you use counterweights to assist the movement, but a winch as you describe will move it easily enough. Just make sure that you incorporate a locking system in the closed position, and thirds or quarters. To secure the roof in a closed position, I'd incorporate a strong metal plate secured to the inside of the roof, that will locate over another plate secured to the wall (like an asp and staple). I'd go the extra mile doing this rather than tethering it with rope, especially if your area is windy.

The solid walls you describe would be better clad in either T&G or overlap to help with stopping leaks, as you state that you want to use flat boards and paint them dark. These will heat up quickly and the expansion and contraction will cause any joints to move more. That way, it will be more watertight, and you can use a thinner ply. Insulate on the inside if you want, but not really necessary seeing as the whole roof will be open! 

Think about a warm room, somewhere where you can warm up, or as the hobby progresses perhaps, somewhere where you can sit and operate a GOTO system via a computer, and not face the coldness. 

There are plenty of pier ideas so I'll leave that.

Alarms. Put one inside so that it can't be readily attacked from the outside, and change the piezo sounder for one with a higher Db, so that it is ear splitting. Something I done in a previous workshop was to have the loudest sounder that I could find, separate from the alarm box sounder. That way they have 2 sounders to deal with. Also have the lights and any electrics inside operate via a master key switch so that they are not easily turned on to help thieves locate your gear. 

These are just my ideas, and what I would certainly look to do, but each to their own.

Good luck with your build.

[mikeDnight]

Hi Jack,

Are there any street lights near by? You mentioned you are 6 foot tall and your walls will be 6 foot high. If you increase the wall height by a further 6" it might just prevent lights catching your eye when you're stood up. I too am 6 foot tall and the 6'6" internal wall height of my observatory works well as a light/ wind shield.

I recently put a new ply roof on my obs and glued a rubber roofing sheet to the ply. The rubber material has a 50 year guarantee and as it drapes over the edge of the roof it creates a skirt that prevents wind and water ingress. Also, there's zero condensation!

Mike

 

 

[SlimPaling]

HI Jack ...

I completed my garden observatory last summer .... it took quite a lot of work (and money) but I got there in the end.

I didn't want to have a roll-off roof as it would take up too much space in my garden so I devised a system where the two halves of the roof hinge out and down to the side of the hut.

I am attaching three pikkies ... the first one shows the structure before the T&G cladding was added. The other two show the roof panels in the open and shut positions ... the roof sections hinge outwards on pivots. They are hand operated and are suprising light to open.

The size of the hut is 2x2 metres and has underground mains electricity and Ethernet cables running into it.

I am well pleased with it.

Mike

[iapa]

1 hour ago, SlimPaling said:

HI Jack ...

I completed my garden observatory last summer .... it took quite a lot of work (and money) but I got there in the end.

I didn't want to have a roll-off roof as it would take up too much space in my garden so I devised a system where the two halves of the roof hinge out and down to the side of the hut.

I am attaching three pikkies ... the first one shows the structure before the T&G cladding was added. The other two show the roof panels in the open and shut positions ... the roof sections hinge outwards on pivots. They are hand operated and are suprising light to open.

The size of the hut is 2x2 metres and has underground mains electricity and Ethernet cables running into it.

I am well pleased with it.

Mike

 

How did you workout the position of the pivot point for the roof?

[SlimPaling]

14 minutes ago, iapa said:

How did you workout the position of the pivot point for the roof?

I worked out the pivot positions on a CAD program .. this allowed me to check how the whole roof panel pivoted and not hit anything else. Quite simple geometry really.

Each roof panel has two separate links and pivot points ... the internal links are used as a stop to prevent the roof going down too far.

Mike

[iapa]

33 minutes ago, SlimPaling said:

I worked out the pivot positions on a CAD program .. this allowed me to check how the whole roof panel pivoted and not hit anything else. Quite simple geometry really.

 

 'suppose it is in a CAD package - never got the hang of them in the '80s

time for the graph paper, protractor and trig tables. 

[SlimPaling]

4 hours ago, iapa said:

 'suppose it is in a CAD package - never got the hang of them in the '80s

time for the graph paper, protractor and trig tables. 

I can probably find some files on my CAD program and put then into a Word Doc to show you the proportions and positions on pivots and links if it would help in any way.

Just let me know and I will see what I can do.

Mike

[iapa]

10 hours ago, SlimPaling said:

I can probably find some files on my CAD program and put then into a Word Doc to show you the proportions and positions on pivots and links if it would help in any way.

Just let me know and I will see what I can do.

Mike

Would appreciate the effort

thanks

[SlimPaling]

2 hours ago, iapa said:

Would appreciate the effort

thanks

I am going to attach a Word Doc showing the main layout & proportions of the pivot points and links. Looking at the photos that I posted before it might not be apparent that, looking at my diagram, the "Blue" links are actually inside the hut and are used hit a stop so that the roof does not drop down to the ground. The "Red" links are external.

Just ask if you need any more clarification.

Mike

How my Roof Panels hinge out.doc

[iapa]

2 hours ago, SlimPaling said:

 

How my Roof Panels hinge out.doc

That's great thnaks.

Diagram is to scale yes?

 

Im planning on a reveres apex double door 8' x 10' as a temp solution this year

 

[Skipper Billy]

You can also work it out with a scale drawing and a compass - draw an arc centred on the desired hinge point of the roof in the closed position - then do the same with the roof in the open position and where the arcs intersect is your fixed hinge point - the distance between the two hinge points just needs scaling up to get the length of the hinge.

 

[SlimPaling]

10 hours ago, iapa said:

That's great thnaks.

Diagram is to scale yes?

 

Im planning on a reveres apex double door 8' x 10' as a temp solution this year

 

Yes ... the diagram is to scale -)

[Star101]

Is the half of the roof heavy? Also, is it leak proof?