Obsy build for the summer...

[fwm891]

Well the model has progressed if nothing else...

Please excuse the panel pin axles, and the brace round the wrong way and... (anything else)

[Yawning Angel]

That is a thing of beauty, well done! It should be on display in the finished build ?

 

[JamesF]

Indeed.  I'm really impressed.  I reckon if you display it in the observatory though you should build another  model at 1:100 and display that inside this model.  Sort of like matryoshka observatories :D

James

[Han Solo]

Francis,

That is a really impressive model, I cant wait to see the full size version!!

James

[Yawning Angel]

Back on the subject of rails: if I were back at the planning stage, I'd be looking at linear guide rails (C-rails) instead of V / C grooved. The guide rails have the advantages of making the roof 'captive', along with being able to keep the rail on the outside so removing the water ingress problem. Looks a little more expensive, but it does remove the need for hold-down clamps and any engineering of your own captive system

[JamesF]

Good point, Alex.  Whilst the simplicity of the round or V groove system has its own appeal, if the construction allows it I reckon they have to be worth considering.

I think we had a poster a while back who effectively did that by using rails intended for putting stuff into the back of a pick-up truck.  Like drawer rails, basically.

James

[fwm891]

I did actually look at the "drawer runner" variant. I looked at the time to take the roof out sideways as the obsy will be rectangular (slightly) narrower one way. I've chosen the twin rails so I can run the roof past the end wall opening a little more sky to the east. I'm still thinking about putting an angled end to the roof above the door but the extra complications in construction and covering out weigh any real/percieved benefit.

Thanks for all the comments - keep em coming...

 

[Astrokev]

Beautiful model!

[fwm891]

Still waiting for the CEM60 at the mo to finalise measurements but finally able to start placement of pegs to locate the corners of the build. Also shown is a section through the proposed wall/floor/foundation area.

I built the model with a square (2000mm) base, that has now changed and will be 2000mm (L) x 1700mm (W). Fixed wall height circa 1220mm, sitting on treated wooden sleepers which in turn sit on blockwork foundations.

Another change I'm looking at is to make the roof run-off rails detachable so they don't encroach on a paved seating area when not in use. I did this once before and the rails will slot into metal brackets at the end of the building.

Francis

[Rusted]

Why not roll off onto the lawn parallel with the fence?
I'd also suggest enough clearance behind the obs. to reach in for litter, maintenance or painting.
Or, make it so close it won't matter but without using the fence for structure.
Putting the obs. so near to the gap beside your house will force some odd manoeuvres with lengthy or bulky objects.
Nor do you want to build so high that you block the light to your neighbour's window.
If they normally have that window open they will be able to hear every sound you make or your mounting slewing. Or vice versa!
External visibility will be high in your present situation through the diagonal gap to more distant homes.
If south is across the rear face of your home then the further away you move the more western sky you will reach.
I would be moving further down the garden for several of the reasons I have mentioned.

[fwm891]

5 hours ago, Rusted said:

Why not roll off onto the lawn parallel with the fence?
I'd also suggest enough clearance behind the obs. to reach in for litter, maintenance or painting.
Or, make it so close it won't matter but without using the fence for structure.
Putting the obs. so near to the gap beside your house will force some odd manoeuvres with lengthy or bulky objects.
Nor do you want to build so high that you block the light to your neighbour's window.
If they normally have that window open they will be able to hear every sound you make or your mounting slewing. Or vice versa!
External visibility will be high in your present situation through the diagonal gap to more distant homes.
If south is across the rear face of your home then the further away you move the more western sky you will reach.
I would be moving further down the garden for several of the reasons I have mentioned.

Hi Rusted,

Firstly the roof will be running parallel to the fence line (no other option) due to lack of space.

The obs will be 300mm from the fence and with the wall height when the obs is open at 1220mm (4ft) it will be easy enough to brush leaves etc away to keep the gap free of debris. Also at only 2000mm long I will be able to push a broom through the gap from outside.

The fence is 6ft high the obs will be about 6ft 6" to 6ft 9" at the top of the ridge (the eves will actually be below the fence.

As to positioning and horizons - take a look at the photo (taken at approx. mount height): I have no north view until I get near the zenith. To the east I have trees that top out at about 50°, to the south I have a small dip in the tree line and to the west my own property is in the way. Believe me I have positioned the obs in the only place I can to get any benefit from the restricted panorama I have. There is a gap between my neighbour and my house which gives me an area of sky to the north west.

If I move east to open the western sky up a little I loose my southern 'dip', If I go west any further I won't be able to go past the meridian when exposing at lower latitudes.

My skies are Bortle 4 and although I have a few street lights around none thankfully shine into the obs position and all are on short posts and well shielded.

As to noise my neighbour is a classical guitarist and practices well into the early hours...

 

[Rusted]

Well, at least you didn't have to build upwards just to be able to see the sky. 

 

Edited May 28, 2019 by Rusted
A lack of perpendicularity ;-)

[mckinnell]

Hi mate, could you tell me what the dimensions are of the main structure, i had a look at your notes but, alas, I could not find them, can you give them in UK not Metric, of the OLD! school and relate most thing measurement wise thus, many thanks.

 

                                                                                                                     Best regards,      Tom.

[JamesF]

4 minutes ago, mckinnell said:

Hi mate, could you tell me what the dimensions are of the main structure, i had a look at your notes but, alas, I could not find them, can you give them in UK not Metric, of the OLD! school and relate most thing measurement wise thus, many thanks.

Based on the post Frances made with his new dimensions I'd say that in old money the base is a touch under 79" x 67" with a wall height of 48".

James

[fwm891]

Hell, spent ages forgetting feet & Inches for the much better metric stuff (I still have ten digits which helps 🤔)

The outside dims of the obs are: 2000 mm x 1750 mm That's: 78¾" x 69" with a wall height of 1220 mm (48"). Walls are 100mm thick (4") Total height 2100 mm (82¾").

The height may change slightly depending on how I suspend the floor. At present my aim is to dig out inside the foundations to give me an air gap under the floor. However I may just raise the wall plates which will increase the overall height by about 100 mm (4"). Time will tell.

Yesterday I began lifting turf and breaking a channel through paving slabs in preps for digging the foundations: Dry postcrete layer under concrete blocks bringing foundations to ground level, then a 200 x 100 (8" x 4") treated sleeper on a mortar bed to remove any inconsistencies in my block laying 🤫. The postcrete will cure by absorbing moisture from the ground and rain - easier to get levels sorted with the mix dry as there's no time constraints.

[JamesF]

Good to hear that you've actually got started now, Francis :)

James

[fwm891]

It's a start....

[fwm891]

Been playing as it's raining....

[MarsG76]

Looks like a great plan.. good luck.

 

[mckinnell]

Francis, thanks for the imperial conversion .

                             Regards,                    Tom.

[Miguel1983]

Hi, 

i've noticed that almost every DIY observatory has a foundation that consists of some smal concrete blocks on witch wooden beams are placed.

I suppose there nothing wrong with this concept, but as a contractor i have to ask, why not pour a concrete slab ?

It might be a cultural thing, i don't now, but here in Belgium every house, shed or what not is on a concrete slab.

Besides the solid and weighty foundation to build on, it's an excellent moist barrier.

 

 

[Swoop1]

I think in a lot of cases, it is to reduce the amount of concrete needed to be mixed.

when you are in the building trade like you are, access to mechanical mixing is probably easier tht for mere mortal like me. If I were to build an obsy, or even just install a pier, mixing would be by hand.

[Bukko]

As above, managing a quantity of concrete is a struggle sometimes and it is tough to mix by hand, even a mixer only partly solves the problem as it still needs to be loaded and unloaded.

Fixing a single concrete slab is also not the preferred solution, as ground movement can transfer to the pier, mount and scope. So an isolated footing is usually installed for the pier.

For my build, I did fit a concrete slab, but this also had a separate, isolated footing for the piers.

When I say "I" I really mean the buulders I brought in to help...

Gordon.

[mckinnell]

Francis, this is a dumb question but, I could not see any reference  as such as to what make of mount/tripod is that in the picture my friend, looks very substantial indeed !!!!.

 

                                                                                                                 Best regards,                       Tom.

[Gina]

Yes, I wondered that too.