Chris's Obsy build

[Chris]

I'm pleased to say that I've finally found an OTA for my obsy on Astrobuy, its a 150p and it comes with all the usual stuff plus both Cheshire and Hotech Collimators all for 140 squids:), so my plan is to piggyback my zs66 on the 150p and use the ZS66 for widefield imaging and as a guidescope for the 150p, the 150p has a bit more focal length and is faster so it might be a bit better on smaller fainter objects once guided. This should tide me over until I can affored a 8" RC or a SW ED120 and the NEQ6 to go with it:D

At the same time as I agreed the sale on the 150p, a chap I know from here put his nearly new SW ED100 on Astrobuy for 450 quid with matched 0.85 reducer, I very very nearly raided the joint account so I could buy it! but this would have meant pulling out of the agreed purchase which is not the done thing:(. I guess on the upside my moral compass has saved me from spending money I don't really have:D

[malc-c]

Chris... are you challenging Gina's record for the longest observatory build thread ?

It's up to 623 posts and all you have is the pipe concreted in the ground Ginal had almost completed her build by the 600th post

[Gina]

[shellfish]

You cant rush perfection lol

[Chris]

Chris... are you challenging Gina's record for the longest observatory build thread ?

It's up to 623 posts and all you have is the pipe concreted in the ground Ginal had almost completed her build by the 600th post

wow! I hadn't really noticed how many posts it was, yeah thats quite a lot! I don't know whether to be impressed or ashamed:o? I'm not mad honest:D

I guess I've been treating it more as a blog and sounding board than a streamlined progress report, I'm not sure if this kind of thing is frowned upon? if so I'll try and be a bit more selective in what I post, I was pretty excited to have finally found my obsy OTA though, had to tell someone:D

Edit:

Wait a minute I'm on 180 posts not 623?? Gina's record is safe she's got more than 1,100 posts and 36,000 views:D

[Chris]

You cant rush perfection lol

If the obsy looks rubbish at the end of this I'll never live it down:D

[malc-c]

Edit:

Wait a minute I'm on 180 posts not 623?? Gina's record is safe:D

-- sorry - should of gone to spec savers !

You are correct....

[Gina]

Phew!!

[Gina]

Using SGL as a sounding board for your ideas seems alright to me - we all have to learn and others may benefit from the discussion

[Chris]

Thanks Gina:)

[shellfish]

LOL

[Chris]

Managed to get out of work early around 3pm so I had a good 4-5 hours of daylight left to get some more done on the obsy:)

I noticed when I dug the pier that most of what I dug out was a mixture of mud, sand, and pebbles which isn't that different to ballast that you buy so I decided to recycle this and use it for levelling the base ready for the slabs which will support the obsy. I now have a fairly level base after a lot of tampering and checking with a spirit level, which is reasonable well compacted but as the ground was so wavey to begin with the ballast base is nearly 2" deep in places so I'm a bit worried about the ballast base subsiding? any suggestions welcome?

one option is to hammer in edging stones all the way around the base, or I have quite a few bricks which I could mortor around the base? I don't want to ballast the whole area as I plan on putting down weed membrane and covering this will green slate chippings.

The pics might explain it better?

[nightvision]

Doesn't look likely there will be much movement, its not as though you are building it in the middle of a lawn on soft earth, looks to be plenty of hard areas nearby to contain the whole thing.

[dtr42]

you could always hire a vibro plate but i dont reckon you'll need to as the slabs plus the batton will spread weight over the whole frame [you tend to get slippage/subsidence when you point load a certain area .As long as you cement your slabs in then should be ok good luck your doing well

[malc-c]

OK I know I went overboard in some peoples eyes when I did my foundations for my observatory, but I can't stress how important having a solid base is in order to keep the structure square and supported, especially as ROR observatories don't have the additional support of a fixed roof.

If you are going to place slabs at regular intervals and then place a decent frame on them (min 4" x 2") then I would recommend digging down 6" -9" where each slab would be and pouring a stiff concrete mix footing on which to place the slab. Alternatively, do as Wayne did and use building sand to support a completely covered block base on which to support the framework for the floor

[Chris]

Doesn't look likely there will be much movement, its not as though you are building it in the middle of a lawn on soft earth, looks to be plenty of hard areas nearby to contain the whole thing.

Thanks night vision, yes the ground is fairly hard below the levelled area so I guess any subsidence would be minor, but I'm now working on a plan to limit that even:)

[Chris]

you could always hire a vibro plate but i dont reckon you'll need to as the slabs plus the batton will spread weight over the whole frame [you tend to get slippage/subsidence when you point load a certain area .As long as you cement your slabs in then should be ok good luck your doing well

Thanks dtr42, ah, is a batton a supporting frame that sits around the raised area?, if so I didn't have one the other day so I was worried that the built up levelled area would eventually slip outwards:icon_eek: I've now placed edging around the whole raised area which should hopefully help:)

[Chris]

OK I know I went overboard in some peoples eyes when I did my foundations for my observatory, but I can't stress how important having a solid base is in order to keep the structure square and supported, especially as ROR observatories don't have the additional support of a fixed roof.

If you are going to place slabs at regular intervals and then place a decent frame on them (min 4" x 2") then I would recommend digging down 6" -9" where each slab would be and pouring a stiff concrete mix footing on which to place the slab. Alternatively, do as Wayne did and use building sand to support a completely covered block base on which to support the framework for the floor

Thanks Malc, agreed I need to have a sturdier base, I was going to sit the supplied shed base on 11 doubled up slabs with morter between them so there would be plenty of space for air to circulate.

I have now placed edging all the way around the base to help stop any of the raised levelled base slipping away, I've also added 6 bags of sharp sand to sit the slabs on plus I've increased the number of slabs to 14 which will all be well mortored in. I also found out that the supplied shed base only sat on 2"x2" or even sometimes only 2"x1" running length ways with 12" centres, so I've now asked if I can have something a bit more substantial and the guy said he can supply 5 extra 3"x2" tanalised timbers which run width ways, so I am now planning to use these and sit them on single slabs but more off them, so similar to Waynes base in a way (he has more area covered but my slabs will be mortored in) I need to both attach the 3"x2" to the base and the slabs to stop the whole thing taking off in the wind:D As well as the tanalising I plan on creosoting the 3"x2" and the base a couple of times. I hope you agree that deep footings won't be needed with 14 400mmx400mm slabs?

[Chris]

Sundays efforts to improve the base: I'll look into adding some more support around the pier:)

[Chris]

Schematic for shed base:

[nightvision]

Should be fine with all that ventilation and heavy engineering!

[malc-c]

I think that based on your plans, you'll be Ok with that base

[Tinker1947]

Not read all the tread, but will you be using any damp proofing between the slabs and the timber floor.

[shellfish]

totaly brill and the edging looks good too

[Chris]

Not read all the tread, but will you be using any damp proofing between the slabs and the timber floor.

Hi Tinker, good question:) I've been trying to decided if I need to as the slabs are spaced for ventillation to keep the timbers dry, and the timbers are tanalised and pressure treated, plus I'm going to creosote them. I wouldn't mind adding damp proof as well, one question though if I wrap damp proof around the timbers where they come in contact with the slabs how should I attach it? I don't want it to back fire and trap moisture against the timber? I was thinking maybe stappling and then running silicon sealant aound the seem, not sure if it sticks to wood though?