Backyard obs planning

[benklerk]

Just need some help and advice.

I'm planning on putting in a 3m x 3m shed to house a GSO 14" RC with either a mesu 200 mount or a JTW mount.

Anyway, Im going with a slab.

Slab first or pier first
How deep to I go with the pier
How high do I make the pier
What is a good size diameter for the pier
How much of a gap do I leave from pier and slab

[glend]

I think a key question is how deep can you go before you hit rock. In the Blue Mtns there is a lot of rock around. Do you know what is under the surface where you want to put the obs. Some might argue for a good solid cubic metre of concrete for a pier footing, but if your pouring it on rock smaller might be better or drill the rock to stick some reo bar in there.
Are you thinking steel pier on a concrete footing or a concrete pier in a form with reo? If a concrete pier, a continuous pour from the footing is best. My pier is a continuous pour, wet on wet. You just leave enough setup time for the last footing pour to support the pier form and pour. I used a big PVC pipe as my pour form and left it in place because it provides a nice finish. Insert your J bars for your top plate as you finish the pier pour. You can buy the J bars at Bunnings, they call them foundation anchors I think, near where the reo stuff is.
I don't know about slab stuff, my obs is on timber posts with the pier coming up through the floor. Houghy did a massive pour, ask him.
Hire a digger. I dug my pier footing by hand, and my post holes, damn near killed me.

[benklerk]

Hi Glen

Its sandstone and clay underneath me, but its starts about 600mm underneath.

Im doing concrete

[xelasnave]

If you can get to rock (any large rock even a large floater but bed rock much better) why not do so.
The one I did at the old place saw getting to bed rock about a meter down..I then cut into it to a depth of about 2 inches.
I placed my pvc pier pipe on that base with some holes in it and placed I think 3star pickets inside..I may have had some wire netting but I am not sure...filled the pipe with concrete with some over the rock floor...I cant recall but wire tieing the star pickets would be a good idea and certainly some stainless steel mess as well...I did not but filling the hole with rock and concrete would be good...if you are going to do it go for overkill☺
Good luck with your project.
Alex

[glend]

When i was building mine i ran across a thread on CN where a guy in Arizona built his footing and pier on rock. He just scrapped the dirt off and used a hammer drill to bore some holes at various angles into the rock, stuck some rebar into the holes and boxed up a footing form around it, and poured into that.

[AndyG]

That, plus some Chemset on the rebar... I can't imagine a home job getting any better than that.

[xelasnave]

In any event one needs the appropriate software to remove vibration in images similar to LIGO ☺ together with gyro scopes on the pier ...
Alex

[Sunfish]

Yep. On a flat site: Hire an mini excavator / two person drill to drill four 350/ 400 holes to refusal. Fill with concrete to 350 below floor level with starter bars. Join with excavated footings . Fully Reinforce and pour slab and footings in one piece. Chemset steel pier to slab. Easier if you know how deep required before you start. So drill / dig a test pit first and/ or ask an engineer for a site classification.

[ChrisM]

Do the pier first - that's the important part. The slab can be poured later with a gap sufficient that the two are not touching - it doesn't have to be large. I left about 15 mm between the concrete pier and the concrete floor of my obs, and filled it with a strip of foam from Clark Rubber.

The pier needs to be 'rock' solid, so your particular circumstances will dictate how deep you need to go. I poured mine in a Formatube cardboard pipe, which is made for the purpose. I dug a 2 cubic metre hole, put in plenty of reo and and had the reo continue up through the tube for the concrete pier. Metal piers are very popular and work well, provided that they are stiff enough. Stiffness comes primarily from the pier diameter, not the material thickness. I used some 6 x 275 mm dia pipe that was readily available. Plenty of others have used smaller diameters, sometimes using tapered gusset plates to provide additional stiffness and also to avoid the pier having a strong resonance at a particular frequency.

The height of the pier needs to be calculated for your particular circumstances, as it depends on your scope, mount, and wall height for a RoR observatory. You need to do some sketches to show how how low and how high the eye piece (or camera) will be over the full range of telescope positions that you will be using.

Good luck with your project!
Chris

[I.C.D]

Hi Have you had look at these it will save you from digging a hole and buying a lot of concrete an reo,andit is equal to a cubic meter of concrete and if you ever move you can retrieve it and take with you Ianhttp://www.surefootfootings.com.au/

[benklerk]

Just an update

I have made changes to my original planning.

I'm now going to go with a timber shed with a colour bond roof, this will be on piers so I won't be doing a slab anymore.

I have attached a diagram which is almost finished of my shed and the diagram of my mount.

The idea is to have the pier 700mm high off the floor and with a wall height at 1.6m and peak inside roof height at either 2m or 2.2m.

At this stage I'm planing on going with a automated roof, it has to move a 3mx3m timber roof.
Does anyone of any ideas what to go with? I would like to keep the motor inside if possible. The motor doesn't need computer control, I'm happy to push a button to open the roof.

Also asking as an idea. If someone who lives in Western sydney that would like to come up and give me a hand this would be appreciated.

Ben