New observatory project!

[Emmanuel Marchal]

Here we go. It's been a long long time I've been wanted to have my own obsy. Having recently (2y ago ) upgraded my scope to a LX200 10",  I found that setting up that scope was no longer a 10 min operation and as a result, my observations got severely reduced to close to nothing. I have to admit I've taken on a full house renovation last year with my family and 2 young children so been quite busy. But now that the house is done, 2016 will be all about getting the garden done and that mean a new shed.... which has to have space for the telescope. The old shed was a simple 7x4, so it makes sense to upgrade to 13x7 doesn't it?! A small spot for the lawn mower and the rest for the scope plus maybe a warm room.

Still working on exact plan and dimensions so I will start posting more soon and keen to get feedback. One thing for sure is I've decided to build it from scratch rather than buy. just much more fun.

One first question is wether i need a concrete slab or concrete foundations or i can simply lay it on top of stone tiles. The garden is well protected so not worried about wind. Thoughts?

manu 

[seo]

Hi Manu,

For a permanent pier/mount installation you'll certainly need a concrete  foundation to support it.

[Emmanuel Marchal]

5 minutes ago, seo said:

Hi Manu,

For a permanent pier/mount installation you'll certainly need a concrete  foundation to support it.

yes, the pier will be in concrete. thinking a 50cmx50cm square, about 60 deep (or at least until rock base if closer than that)

[seo]

In my opinion, you'll need way more that a 50cmx50cm concrete base, at least 1 m. I'm not talking about the pier itself, I'm talking about the base.

So, depending of course on what mount and telescope/s setup I'll install there, If I was in your position I'd make the base concrete at about 1,30cm X 1.30cm and as deep I could go.

[Physopto]

More concrete the better. Deeper the better. One way of saving money is to use reclaimed (but clean), bricks or old broken concrete to mix in with the new concrete as you fill the hole. You can save up to 25% approximately without loosing strength of the foundation. Also if you back fill as you fill the hole so that it resembles a pyramid but with flat top. The ground then adds weight to the foundation. Saves a fair bit of money in the end. I would add a cement/concrete waterproofer though such as Sika 1.

 Best of luck,

 Derek

[Emmanuel Marchal]

On 2/2/2016 at 19:20, seo said:

In my opinion, you'll need way more that a 50cmx50cm concrete base, at least 1 m. I'm not talking about the pier itself, I'm talking about the base.

So, depending of course on what mount and telescope/s setup I'll install there, If I was in your position I'd make the base concrete at about 1,30cm X 1.30cm and as deep I could go.

planning to have my LX 200 10" with EQ6 so a fairly good amount of weight

Given input, i will increase size of pier base.

 

[Emmanuel Marchal]

On 2/2/2016 at 23:21, Physopto said:

More concrete the better. Deeper the better. One way of saving money is to use reclaimed (but clean), bricks or old broken concrete to mix in with the new concrete as you fill the hole. You can save up to 25% approximately without loosing strength of the foundation. Also if you back fill as you fill the hole so that it resembles a pyramid but with flat top. The ground then adds weight to the foundation. Saves a fair bit of money in the end. I would add a cement/concrete waterproofer though such as Sika 1.

 Best of luck,

 Derek

Good ideas. I'm also having a large patio being done as the same time and there will be a lot of old brick and broken concrete as a result. good way to avoid sending too much to the skip!

[Daniel-K]

5 minutes ago, Emmanuel Marchal said:

Good ideas. I'm also having a large patio being done as the same time and there will be a lot of old brick and broken concrete as a result. good way to avoid sending too much to the skip!

you dont need a huge hole that goes all the way to auz. mine was about 3ft x 3ft and 3ft deep. i used some air duct of ebay cost me about £17 250mm diam. i then used old rebar hammered it down into the ground where the center of the pipe would sit. 

packed the bottom of the hole with smashed bricks to keep the pipe level and filled the hole and pier with concrete. 

look at that graph it says it all 

building an obsy is great fun aslong asyou make a floating floor around the pier so no vibrations transfer to the pier your fine.  good luck and have fun !!!

[Emmanuel Marchal]

Thanks Daniel. the airduct idea is great one. though i already have a pier which I bought for about the same price from the person I acquired the lx200 from!

3ftx3ftx3ft. that is a pretty big block of concrete. i'm sure that would be stable!

 

[Physopto]

The idea of the pyramid type concrete support is three fold one that the ground helps to anchor the support down as it adds cost free weight the other is that the cut off top of the pyramid is smallish (you pick the size to suite). Having a smallish flat top means you tailor it to just bigger than you need for the pier.  That way you don't tend to stand on the pier support as you move around in the observatory. Your poured concrete floor can sit over but not touching the pier directly, separated by softish foam. Or if a wood floating floor it allows plenty of clearance to help your build. Lastly cost saving. 

As I say best of luck,

Derek

[Emmanuel Marchal]

4 hours ago, Physopto said:

The idea of the pyramid type concrete support is three fold one that the ground helps to anchor the support down as it adds cost free weight the other is that the cut off top of the pyramid is smallish (you pick the size to suite). Having a smallish flat top means you tailor it to just bigger than you need for the pier.  That way you don't tend to stand on the pier support as you move around in the observatory. Your poured concrete floor can sit over but not touching the pier directly, separated by softish foam. Or if a wood floating floor it allows plenty of clearance to help your build. Lastly cost saving. 

As I say best of luck,

Derek

very good points. i think i'll do this!

[Physopto]

If you want to do it, the easiest way is to make a pyramid out of something like 12mm particle board. The hole at the top is the size you want for the pier to either bolt on to or to sink it into the wet cement. A couple of cheap flat bent metal furniture fittings can be used to hold the sides together. When filling it with the concrete and broken bricks etc, you will need to weigh it down with plenty of old bricks, concrete or soil. Otherwise the former will be pushed up by the mass of the concrete as it is filled. The beauty of this is after a couple of days you can remove the bricks etc, and the particle board. You then have a clean flat surface to line with expanded polystyrene foam to act as vibration insulation. Then just back  fill again with earth. If you sink a post for a pillar into the wet concrete just have some bracing wood ready to support it before you start. If you are going to fit a made pier with a flange at the bottom you can either sink Stainless Steel of the correct size (with a bent end as an anchor) into the wet concrete. Just make a particle board copy of your flange to act as a positioning template. You can use it to level the concrete top.

I haven't done this for a pier, but it is my intent. I have done it with about twenty 4" angle iron steel garden fence posts 9 foot long I put in over thirty years ago. They were sunk two and a half feet into the concrete. None have moved, even when accidentally hit by some idiot with his hired white van.

Anyway have fun, I will be eager to see your progress.

Derek

[Emmanuel Marchal]

thanks Derek! do you mean putting the foam just on top as per drawing here?

 

[r3i]

Best of luck with your build and look forward to seeing how it progresses.

Yes, you have to have a decent amount of concrete in your pier base but there's no need to go over the top.

My pier base (which has an EQ6 atop of it) was 45cm square, 60cm deep into the ground with about 30cm above ground and strengthened with a fair few bits of rebar - it has been as solid as a rock.

As for the base for the observatory itself, there's plenty of options and a browse through previous build threads will give you some ideas.  I went for building mine on top 10 MetPost anchors - this was a good solution for me as there is a slight slope to our garden and it made it easy to level the observatory base.  I also didn't want to have a massive slab of concrete in the garden for posterity.

[Physopto]

Yes that is the general idea. Just make sure that the foam is between the observatory floor and the pier support. Best is you pack the lower pier support in tight with the soil and backfill. The foam only needs to be between anything you can stand on so as not to transfer vibrations. i.e not al the way down to the bottom of the pyramid. Once it has been a very short time the soil settles and gets wet etc, so it compacts and just glues the whole thing down. You can wet (flood) it with a hose after a day or so and it speeds things up.

Nearly forgot make the pyramid top about 6 inches bigger than the pier base for strength.

 

Derek

[Emmanuel Marchal]

all good thanks!

[Emmanuel Marchal]

3 hours ago, r3i said:

As for the base for the observatory itself, there's plenty of options and a browse through previous build threads will give you some ideas.  I went for building mine on top 10 MetPost anchors - this was a good solution for me as there is a slight slope to our garden and it made it easy to level the observatory base.  I also didn't want to have a massive slab of concrete in the garden for posterity.

Really glad you mentioned this. I've been struggling with the idea of a concrete slab or foundation. and what you have built is so close to what i am planning for. only exception is i need an extra room in it as a garden shed (for the mower ;))

would you have a plan of your obsy to share by any chance?  cheers

[Ken82]

A concrete base is essential I learnt the hard way  I eventually ripped the ground up and poured a 5" concrete base . Stupid mistake for a civil engineer but let's just say it's not your average building ! 

[Davey-T]

I think a huge concrete base is unnecessary my LX200 pier has 75mm angle iron legs buried in 400mm X 400mm square by 400mm deep concrete, this perfectly suitable for visual and for imaging no amount of concrete will stop vibrations, just try jumping on the ground outside your obs'y while videoing Jupiter
especially at the focal length of the LX200

I think the huge square of concrete was originally invented by our American cousins in the frozen parts of the USA to combat heave caused by frozen ground, something that we in the UK are unlikely to suffer from.

Just my 2d 

Dave

[Emmanuel Marchal]

12 hours ago, Davey-T said:

I think the huge square of concrete was originally invented by our American cousins in the frozen parts of the USA to combat heave caused by frozen ground, something that we in the UK are unlikely to suffer from.

made me laugh... I think I'm heading for a 500x500x500 pier base or as much as the ground will allow me... maybe bedrock is much closer than i think...

[Emmanuel Marchal]

13 hours ago, Ken82 said:

A concrete base is essential I learnt the hard way  I eventually ripped the ground up and poured a 5" concrete base . Stupid mistake for a civil engineer but let's just say it's not your average building ! 

you mean for the pier or the entire obsy structure?

[Davey-T]

2 hours ago, Emmanuel Marchal said:

made me laugh... I think I'm heading for a 500x500x500 pier base or as much as the ground will allow me... maybe bedrock is much closer than i think...

That'll be the Kent Ragstone I expect, I could do with some more for my rockery if you dig some up

Dave

[Ken82]

Just the pier  I have timber floor in the observatory which has a gap between that and the concrete pier base to prevent any movement 

[Emmanuel Marchal]

On 2/6/2016 at 21:19, Ken82 said:

Just the pier  I have timber floor in the observatory which has a gap between that and the concrete pier base to prevent any movement 

ok. that's what I'm aiming for. pier has to be rock solid.

[Emmanuel Marchal]

On 2/6/2016 at 10:59, Davey-T said:

That'll be the Kent Ragstone I expect, I could do with some more for my rockery if you dig some up

Dave

 I'll let you know!