Idiot level observatory questions....

[kirkster501]

Hello folks,

I am going to embark on an observatory build but have some [very] basic questions please?

I will build a pier.  How deep should this be ideally?  The consensus appears to be about 20 inches?

I may be moving home in three years or so.  I don't want the "floor" of the observatory to be a concrete slab.  I would rather build the floor out of wood so that the new occupants don't have  a huge concrete slab to have to deal with.  Any others do this?  How did you firm up the wooden floor onto the earth below? Or am i worrying too much about this do you think?  The obsy will be built very tastefully so for viewings.

Regarding the pier.  Is it best to buy one of the steel ones or make your own from drainage pipe?  Again, I'd want the surface concrete of the pier block to be six inches below ground so that all traces of it could be removed in the future and just turf over the concrete block.  How do you anchor the pipe?  Do you just stuff it to the bottom of the hole and pour concrete all around it?

Sorry for basic questions that may be answered in some other threads.  I am going to get googling on this subject  I'd wan this done ideally for prime galaxy season if possible.  I am a good DIY'er.

Thanks. Steve

[wxsatuser]

Basically I built a deck on concrete surrounds, the concrete is about 6inches deep by 4inches wide.

The pier is a cube about 24inches or so.

[jnb]

Depth of foundations for the pier will depend on your local soil. Not wanting a concrete slab for the observatory floor is an advantage. Construct a deep solid foundation for the pier, this might be only a meter wide. The observatory will not actually touch this. The observatory building can sit on shallow foundations or piers so it can be removed in future. The observatory floor can then be suspended on joists between the piers and surround but not touch the pier. As it does not touch the pier it does not need to be that firm.

The only part you need to construct that will not be easily removable is the foundation for the pier. If you want that to appear removable then you will need to go deeper to get the same mass to support the pier stably and have a longer pier. i.e. instead of attaching a 1m steel pier to a concrete block protruding above the ground attach a 1.5m pier to a concrete block below the ground.

[m37]

I think vibration and stability are your main enemies here. Putting a tripod on a wooden floor would send vibrations through it every time you move around. How about a wooden floor around a central concrete post? At least then they would only have to tackle a small ish concrete block in the event of wanting to remove it.

[DaveS]

Thinking about a pier, is there any mileage in making it from engineering bricks? I'm thinking that you could build it to the required height, then when you move just knock it apart below ground, at the level of the block.

This is something I'm thinking of for my own 'scope, though not yet an obsy.

[Tinker1947]

When i built my Obby i didn't want to mix cement the hard labour isn't something i wanted to do again so i dug some holes for the posts and held them in place with pea shingle used a bag a post cost £3 a bag, i also made a wooden pier it 6" X 6" oak and went in a 4' deep hole again held in place with shingle the oak pier cost less than £100 including the 16mm studding, nuts and washers, as your moving some time in the furture the pea shingle can be hoovered out with a industrial hoover, you could build a Obby then remove all traces and take it with you when you move....some pictures.....

4' Deep holes really depends on your ground mine is soft silty stuff

Floor Joists coach bolt so they can be removed....

The Floor

The Pier

The Outside

This might not be the best way to build a Obby but it can be taken down and moved, just depends on the size you want ect.....

[nmoushon]

I'm in a similar boat as you. Not sure how long I;m going to stay in my current house so don't want to leave a huge foot print for the next owners to deal with or the possibility of lowering the value of my house. So what I'm planning is digging and pour a 6"x36" diameter footings in each of the corners. I would also dig a 12"x36" diameter footing somewhere for my pier base. All are inset into the ground about 6" or so.  I would then attach at least 4x4 posts on all the corners to the corner footings and then build my slightly raised wood floor from there. Of course leave the space for the peir. If you ever move you can design the obsy to be taken apart so that you can take it with you. You then can just push dirt back over the footings.

Like said above the depth of your pier base and footing depends on your soil and your climate. Where I'm at I intend to dig below the frost line which is between 32-36". If you dig below this you will prevent any movement to the and freezing/thawing of the ground during winter. I don't think most of Britian gets that cold so make sure to do some searching to find your frost depth or get some examples from people who have built in areas similar to yours.

[Peter Drew]

I go about it in a different way (as usual). The pier for my 220mm F12.5 refractor has a freestanding base  made from 5 600x600x50 concrete paving slabs, 4 arranged in a square and the 5th placed central on top of the square and bolted to each of the 4 slabs. The pier itself is made of pairs of concrete building blocks about 2m tall. The floor of the obs is supported on the wall foundations and at no point touches the pier. Steady as a rock! 

[red dwalf]

I built my obsy on paving slabs, cemented onto hardcore, pier was a 8 inch drainage pipe filled with.concrete, all of the build is shown on my website which can be accessed via my signature below, the obsy was all screwed together so can be dismantled if needed.

[lunator]

I go about it in a different way (as usual). The pier for my 220mm F12.5 refractor has a freestanding base made from 5 600x600x50 concrete paving slabs, 4 arranged in a square and the 5th placed central on top of the square and bolted to each of the 4 slabs. The pier itself is made of pairs of concrete building blocks about 2m tall. The floor of the obs is supported on the wall foundations and at no point touches the pier. Steady as a rock!

Hi Peter

Can you post a pic?

Something like this could work for me

Cheers

Ian

Sent from my iPod touch using Tapatalk

[RikM]

I'm going for a standard pier construction using 160mm PVC waste pipe filled with concrete. Since it will be quite tall, I plan to drop it quite deep into the ground and drive some angle iron into the bottom of the hole to anchor it further. I plan on at least 600mm deep but it depends on how soft it is down there. The plan is a 2m tube so 600mm deep, plus 220 for the floor frame and supports leaves me with 100mm clearance from the roof with the scope parked horizontal. I have a 3m tube, so can cut to length depending on what I find at the bottom of the hole.

My current plan for the obsy footings is to sit it on 100mm foundation blocks sunk into the ground, so there is no contact between the obsy and the pier.

[Clockwork_Orange]

I went for a steel pier and bolted it to my obs floor, I got a local steel fabricator to knock one up for me out of 6 inch mild steel with flanges welded top and bottom, cost £95.00 and they even painted it for me at no extra. I also got them to drill a blank flange to enable me to bolt the mount to the pier. It is solid once bolted in place I have got the option of filling the pier with sand to deaden any vibrations, but to be honest I don't think I'm going to need to do that. Should I ever decide to move 4 bolts and it's gone

Sorry if the orientation of the photo's is wrong, sent from my iPad

John

[r3i]

Hi Steve,

 

My observatory is built upon decking which has been fixed to the ground with 10 4" Anchor Posts (aka MetPosts). Theses have been additionally secured with concrete but the overall concrete footprint is minimal and removal shouldn't be too onerous.  I was of the same opinion that I didn't want a huge slab of concrete being left for future generations.

 

My pier base is about 24" underground and 12" above.  Someone on another thread had a clever idea of digging out a big enough hole next to the pier so that the pier could be pushed over and buried if ever required to do so.

[todd8137]

Nice work I love my pier and home built obsy

Pat

[kirkster501]

Thanks guys, some great ideas here.  I particularly like the idea of using four posts in concrete, similar to fence posts I'd assume, and put the buildign up around those.  How far did you go down for these?

So some further research now on how to attach a roll-off roof.  What about a fold over roof to reduce the ground footprint? And how to build a door to get in! ??

Thanks, Steve

[nmoushon]

Thanks guys, some great ideas here.  I particularly like the idea of using four posts in concrete, similar to fence posts I'd assume, and put the buildign up around those.  How far did you go down for these?

So some further research now on how to attach a roll-off roof.  What about a fold over roof to reduce the ground footprint? And how to build a door to get in! ??

Thanks, Steve

Look up bat-wing or gull-wing observatories. Should give you an idea of what most people do.

[Davey-T]

Made my obs'y from Keter plastic shed on paving slabs, 8" square steel pier mounted on four 3" X 3" steel legs buried in 18" of concrete , roll off roof is easy as it's very light, if I wanted to move house it could all be flat packed in a couple of hours.

Dave

[Bubbles82]

I would just like to say that no question is stupid. when it comes to the people on this forum there are always people in the know will to try and help that's what makes me visit several times a day

[ChrisLX200]

Maybe my pier is a bit OTT but it is 8" ID steel steam pipe with a 3/8" thick wall, and rather than try and cut the length that was given to me I had to sink 5ft 6" of it into the ground, after first digging a 5ft diameter hole a bit over 6ft deep and lining the bottom with about 8" of concrete.Then the pipe was stood upright on that, levelled, and the hole filled with about 4 tons (?) of concrete. I don't think it's going anywhere...

ChrisH

[beamer3.6m]

Davey do you have pics of your obsy as considering plastic shed also.

[laser_jock99]

Set your pier foundation low enough so that it can easily be 'buried' when you move on. The bolt down pier you can then take with you.