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Old 26-11-2022, 05:06 PM
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Loupy31 (Peter)
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Home Observatory Build

Hi Everyone,

Ok, I have been given the ok to build a small observatory in the back yard.

Because we live on a sloping block, The floor Hight from natural ground, where the pier will be, is 530mm, What I need to know, is how deep, wide, is the minimum I will need to dig for the pier support,
There are many question i have, but To make a start, doing the concrete is the first thing that needs to done.

any ideas are most welcome.

Cheers Peter
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Old 26-11-2022, 09:18 PM
glend (Glen)
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Depends on how you build it. In my opinion, pouring your pier as part of the footing is the easiest (and how I did mine). The actual dimensions of the footing depend on your soil type, the weight you expect it to hold (mount, scope, other gear, etc). You will hear people argue that a cubic metre is ideal, but really that is over kill for most amateurs. Anything from 60cm x 60cm x 60cm and up from there can be fine, if you drive star posts, or angle iron, reo, etc into the ground as anchors before you pour the concrete. You also need to think now, about whether you ever want to remove it, and ground anchors maje that more complicated.
As to the structure itself, my pier was poured (with reo) in a plastic pipe form, wet on wet in other words as soon as the footing is firm enough to support the pier pour. Brace your pier form to the vertical. Lazy people may prefer buying a custom made steel pier and attach it to a flat top pier, this will cost you more. Don't forget to insert your top bolts into the wet concrete, you can buy foundation L bolts at Bunnings that work fine.

My pier rises up through the floor of my observatory (without touching it). The observatory is also on a sloping block, but his set on treated posts which are supporting the level floor (posts set in concrete). I encourage traditional timber stud wall construction, as it's easy, and it will not sweat like metal buildings, or become a sauna when the sun is out. Roofing is worth thinking about now, draw it up, again colourbond is heavy as he'll, but polycarbonate corrugated roofing is very light, generally hail proof, and easy to work with. Have fun.

PS, take the time to find out what local Council rules might affect your plans. In NSW, if you keep it fairly small, no Council approval is required, nor inspection. Basically just claim it is a garden shed. Not sure about SA.
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Old 26-11-2022, 09:24 PM
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Can you get to bed rock?
If so key it in and you will be fine.
I always frankie pile for my pads, ie driving star pickets in (4 to 6) at 45 degrees into the ground and have the ends extend into the pad..that makes for a very stable pad ...my last two pads each only contained around 15 bags of ready mix..one carries an EQ8 the other only EQ5 ..these are three piers to support tripods But the third set up is a central pier which used the same star picket approach and it carries an EQ6. Being on slopping ground makes frankie piling mandatory in my view help stop it going down hill..but I don't think others bother...but only because they don't think about it I suspect.

Edit..Glen does it and you can trust him.
Alex
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Old 27-11-2022, 09:03 AM
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Loupy31 (Peter)
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Hi Guys, thankyou for all that info,
The star posts idea Is new to me,

So After I dig the the footing for the pier, I just go ahead and hammer
the Star posts into the bottom of the hole, angled, As far as i can get them.
So they actually act like a wider footing .

Thx soo much guys

cheers Peter
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Old 27-11-2022, 09:08 AM
LonelySpoon (Neville)
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Probably not an issue in SA, but you need to get below the frost line.

As Alex says, bedrock is best.

I'd suggest also making the pier and base bigger than you think you need, in case you eventually want a bigger mount/scope.

A cubic metre is a lot of concrete, and probably overkill, especially if you reach bedrock. I've used 600m cube in the past for an EQ6 head, but my EQ8 has a huge base.

In the past I've used 6" terracotta drainage pipe with the wide collar at the top, filled with concrete. Looks good and can be used as a bird bath if you want to move on (seriously).

Neville,
LSO
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Old 27-11-2022, 10:45 AM
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Ok, Silly question, how do I know when I have hit Bedrock?
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Old 27-11-2022, 10:52 AM
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mura_gadi (Steve)
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Quote:
Originally Posted by Loupy31 View Post
Ok, Silly question, how do I know when I have hit Bedrock?

When the shovel comes up bent... or you need a pneumatic hammer to get any further, either of those would be good signs.

Ps. Don't forget about any power or data requirements you might have.
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Old 27-11-2022, 02:53 PM
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There could be rock ..it may not be bed rock so the test is to drive a crow bar onto it...bounce it up and down..if it is a floater it sounds dull, if bed rock it has a sharp sound..after probably half a dozen holes and checking rock you will tell the difference easy ...however if the rock is so big that you can not tell if it is a floater or not it really does not matter just key into it...
The star pickets top protrudes into the area that you will pour your concrete and so they project out into your pad enclosures but not beyond the final pad pour...have an angle grinder on hand in case you can't drive them all the way in ...you can cut 5hem off rather than banging away forever..if you choose to pour your pier using a pvc tube which is in my view the best way you can place four star pickets in the tube before you pour and even drive them into the ground.
I would be happy to have a floor with air under rather than a pad on the ground as a pad on the ground can hold heat whereas a floor space allows thermal equilibrium to be reached easily.. so make sure you have ventilation.
Alex
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Old 27-11-2022, 03:35 PM
dikman (Richard)
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Quote:
Originally Posted by Loupy31 View Post
Ok, Silly question, how do I know when I have hit Bedrock?
Alex beat me to it, if the crowbar bounces back up out of the hole you've hit rock! It will bounce really well if you hit quartz, not quite so well with shale - but at least the shale can be broken up, albeit slowly and with a lot of effort.
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Old 27-11-2022, 04:32 PM
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Loupy31 (Peter)
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LOL, Thx guys, I will be going to bunnings later this week and hopefully begin some marking out, I will try and take a few pics, before, during and after.

Cheers

I will make sure I have a conduit for power and a separate one for Data, through the footing and pier
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Old 29-11-2022, 05:32 PM
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Loupy31 (Peter)
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Hi Guys,

I have decided to go with a full concrete pier,

Does any one know where i can get a length of the cardboard tube for the pier

In South Australia would be preferred.

Cheers peter
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Old 29-11-2022, 06:29 PM
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Cardboard probably will not work as the wet concrete may destroy it's integrity and it could deform or even collapse...if you do go that way paint the inside and outside of the tube to make it water proof...a couple of times

If you go for cardboard do not use wet concrete..put it in dry and let the thing draw in moisture from the ground..that's what I do and days later give them a hit with a squirt bottle..not much mind you...then more the next day...there is a case to suggest it is stronger doing it dry and slowly letting it gain moisture..look it up.

What you need is a PVC pipe...sometimes you see ones that telecom have abandoned...but go for PVC..or steel...my triple piers..one has steel piers and the other has PVC...

You can also make a box section pier using ply ...Actually I have made a pier out of just ply and fibre glass which worked well.

Bite the bullet and ask Bunnings..I think 225 mm is what I last used.

Alex
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  #13  
Old 29-11-2022, 09:02 PM
TrevorW
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You can buy form tube



https://formdirect.com.au/formwork/c...ormwork-tubing


https://www.yousta.com.au/product/ez...forming-tubes/




if you lucky try a construction site they may have some scrap
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