Samtheeagle's Nest

[samtheeagle]

This summer will hopefully see the construction of my observatory! I've got the all important wifal approval, some steel tubing for a pier, and enough money get get me started i.e. to buy a shed and some other materials. I've spent many an hour browsing through the various build threads, and the thing I keep reading is how important it is to plan... So in that vein my first big decision is where to locate the observatory.

I've a long thin garden that runs east to west, and there are a number of places where the obsy could go, but they all have view obstructions of one kind or another. I was hoping that someone could advise me on what is generally considered to be the "best" viewing direction(s) to have clear? I have 3 options available to me:

1. Near to the house. The view to the east is completely blocked, and the obsy would be build on a concrete base that's there. Other views are pretty clear.
   
2. Halfway down the garden. Good views east and west, but north and south are somewhat nerfed by trees in neighbours gardens.
   
3. The far end of the garden. The west is completely lost to a row of tall trees, but the other directions are relatively clear.
   

My gut feeling is #3, but it is the closest to the train line, which could derail a few of my subs But to be fair, using my kit up by the house will pick up some wobbles when the heavy freight beasts rumble through late at night

What do my learn'd friend think about my options?

[iwatkins]

Ahhh, the where to put it question.

Tough call.

But I would also go with #3. If you only lose east or west, that would be fine with me. Just about everything will be visible at some point in the year.

Only other concern would be mains power if you need it?

Cheers

Ian

[samtheeagle]

Yes, I'm definitely going to want mains power to the obsy. It'll be soooooo nice not to have to keep watching the battery meters to see how much longer I can keep imaging for Fortunately my father-in-law is a sparky, so other than the cost of a faily long length of armoured cable, and some significant trench digging that's not a major concern for me. Speaking of which, I need to figure out what kind of ampage cable I'm going to need. Better start adding up all the things I'll be running off it

[Gina]

I went for the 23A cable for my obsy, not just for the current carrying capacity but to avoid voltage drop on a long run when running a fan heater at 2kW for the warm room in the winter. Anyway, you have a sparky on hand to advise you

2.5mm2 3 Core Steel Wired Armoured Cable - Cable - Electrical -Tools, Electrical & Plumbing - Wickes

[samtheeagle]

Cheers Gina, that's the kinda of value I was guestimating I'd want. What length of cable run did you need?

[sologuitarist61]

!'d prefer a southerly site taking in a bit of east and west. There is much going on to the north but, to my mind, more in the south.

[iwatkins]

Also consider running some cat5 cable in the trench as well. You may never use it, but it is there in case you want to monitor/image from the house.

Cheers

Ian

[samtheeagle]

Also consider running some cat5 cable in the trench as well. You may never use it, but it is there in case you want to monitor/image from the house.

Cheers

Ian

That or make use of those rather nifty ethernet of mains devices...

[Gina]

As it turned out I only needed about 10 metres of armoured cable as I only took it into the back porch rather than all the way to the fusebox. So I could have bought a shorter length. Doing it that way meant an RCD and switch in the porch with standard T&E to the fusebox. I also have an RCD plus CBs for power and lighting circuits in the obsy (a garage type consumer unit) - so everything is well protected.

[samtheeagle]

Thought it might be a good idea to nip out with a camera to build up a panoramic view from the point where I'm planning on putting my obsy. Simple point and click affair, with the pictures taken from head height...

http://www.guywebb.co.uk/astro_images/ObsyView.jpg

Gives you an idea of the views I'll be getting, looking back towards the house is east. There are a few obstructions, but nothing massive. The view north is a bit blocked by trees, but they're not all that tall. So long as I can see polaris ok from down there I'll be fine. It looks worse than it is in the pics, as I've taken the snaps parallel to the ground...

[Gina]

Interesting That's a good panorama.

I have some views all round that I took at my pier position before building my obsy but never got round to stitching them together. Think I'll have to mount camera on my scope and do an all round set of photos to make a panorama.

[Tinker1947]

Southerly view will show DSO that never make it to the north, my workshop has Armour cable(40amp) as a power source shovel proof provided its not JCB type shovel..)

[samtheeagle]

I've enhanced my panorama and made it into a custom landscape for Stellarium Very handy indeed, I'll be playing for hours to see what sort of views I'll get at various times of the year. I'm mildly converned about my view of polaris from the proposed location. It's fine at the moment, but another few feet of growth on the neighbours trees and I could be stuck :S

[martin_h]

I've enhanced my panorama and made it into a custom landscape for Stellarium Very handy indeed, I'll be playing for hours to see what sort of views I'll get at various times of the year. I'm mildly converned about my view of polaris from the proposed location. It's fine at the moment, but another few feet of growth on the neighbours trees and I could be stuck :S

But the advantage of a perminant setup is you only need to see polaris once , when you put the mount on the pier! And even if you cant see it you can point in the rough direction and drift align.

[laser_jock99]

I went for the 23A cable for my obsy, not just for the current carrying capacity but to avoid voltage drop on a long run when running a fan heater at 2kW for the warm room in the winter. Anyway, you have a sparky on hand to advise you

2.5mm2 3 Core Steel Wired Armoured Cable - Cable - Electrical -Tools, Electrical & Plumbing - Wickes

We went for 6.0mm2 cable. Although the same cable takes power to the work shop where I run power tools etc (but never at night!). Probably overkill for the obsy but necessary for the adjoining workshop.

[samtheeagle]

I'll have to wait and see what my tamed sparky says... The garage currently has mains power out to it, and I would be looking to extend from there out to the obsy. The current garage wiring is, errrr, "interesting". The previous owners weren't too worried about quality signed off work it seems. So yeah, the run out to the garage might require an some meatier cable, but on out to the obsy wont need anything quite so hefty.

Most of the gear will run from my newly acquired bench power supply, and then there will be a laptop, a light and a dehumidifier. I can't see that little lot drawing anything like 23A

[samtheeagle]

So I find my next big obsy decision is do I convert a shed, or build from scratch? Initially I was planning on converting a pent shed, a good quality one, tongue and groove shiplap, with double frame and what not. But having trawled through some of the other build threads I'm getting concerned that it wont be sturdy enough. And if I'm going to have to build an interior frame to strengthen it up, I'm not that far away from a custom build from the ground up. And a custom build allows me to make it whatever size I like, and I wont have to work around any issues with how a purchased shed is put together.

The shed I was looking at costs ~£330 for an 8x5. I guess what I really need to do is price up the materials required for building my own to see how it balances out.

What are peoples opinions on converting sheds? When I first started reading up on building a roll off roof obsy, converted sheds seemed to be the preferred choice, but more and more people are doing bespoke builds it seems. Is this advisable? Or is it more of a nice to have? For me, my obsy needs to provide the following:

1. It must be waterproof, and therefore safe to leave my gear setup in it.
   
2. It must be quick and easy to open up so I can make the most of the rare clear skies.
   
3. It must have mains power.
   

That's about it. Nothing flash, just a utilitarian workspace to allow me to enjoy my hobby as often and as easily as possible. I'm really not that fussed about a warm room, that seems like a luxury I can easily live without. I'm not even worried about being a bit cramped in there. Having my kit ready to start imaging within 5 minutes, instead of the current ~1 hour setup time, is what I'm looking for.

[dmahon]

Can you go to 8x6? 8x5 might be a bit cramped?

[Tinker1947]

Material prices, back in April 2000 i purchased 12 sheets of external ply 8' X 4' they were £10 a sheet, went in the same building supplies today ask for the price of said sheets, £46 each i dread to think what a diy well made shed would come to...

[samtheeagle]

Material prices, back in April 2000 i purchased 12 sheets of external ply 8' X 4' they were £10 a sheet, went in the same building supplies today ask for the price of said sheets, £46 each i dread to think what a diy well made shed would come to...

Yes, that is my concern. Having recently made some staging to go in the wife's greenhouse I'm all too aware of timber prices But perhaps a "proper" lumber merchant will beat the pants off B&Q/Wickes etc? I need to settle on a size and then try to calulate what sort of volumes I'm talking about... I probably could push to 8x6, I'm not exactly short of space, but the wife will only tolerate so much of an intrusion

My high level plan at the moment, whichever way I decide to attack the build, is this:

• Simple foundations of a half dozen concrete blocks which will be sunk into the ground like the pier base, but a good bit smaller. To these a raised wooden frame can be attached with a vapour barrier to help prevent rising damp.
  
• An outer shell of shiplap tongue and groove, either a purchased shed, or custom made panels. This outer shell will have a vapour barrier affixed to its interior faces.
  
• An inner skin of OSB perhaps? Just some thin-ish (~10mm?) panels. This I hope will make things more sturdy, more damp proof, and more pleasing to the eye.
  

Then of course I have to figure out the roll off roof aspect, but a lot of that will depend on the type of build I go with, so I'll get to thinking about that later when I have a few more things decided.

Anyone pick out the fatal flaws in my plans so far? Best to nail them now me thinks!

[Gina]

I found our local timber merchant was just over half the price of Wickes and far better quality. B&Q are even dearer than Wickes I found. Wickes are a good price for many thing but NOT timber. DIY stores in general are very expensive for timber.

Vapour barrier wants to go between shiplap and framework.

I used 6mm exterior grade plywood on a timber framework for my ROR covered with rubber roofing - the lightest system I could devise. I used 6mm plywood to line my warm room too. The scope room is unlined. OSB needs to be thicker and therefore heavier for the same strength as plywood. Plywood has a much nicer surface than OSB and even looks good varnished.

I used 6 poured concrete blocks for my floor supports too with good solid floor supports and T&G wooden flooring. Warm room has polystyrene insulation under floorboards and in all walls and roof.

Of course, bigger is better for the obsy but I know other conditions apply.

[samtheeagle]

I found our local timber merchant was just over half the price of Wickes and far better quality. B&Q are even dearer than Wickes I found. Wickes are a good price for many thing but NOT timber. DIY stores in general are very expensive for timber.

As I suspected. Thanks Gina. I shall have to do some shopping around to see what my local options are. Urgh, so many decisions to be made! It's hard to know where to start

I'm glad to see that my foundations idea isn't totally wrong, that was a bit of a flier to be honest. As I said before, the size of the obsy isn't my biggest priority, having a secure and dry setup ready to roll at a moments notice is what I crave

[samtheeagle]

Following starfox's thread (http://stargazerslounge.com/diy-observatories/183685-chriss-obsy-build.html) the idea of a metal shed was raised. This was one of my first options, but I discounted it on the grounds of how hot I imagined it would get during the summer months, or any good sunny day for that matter. But bizibilder has reported that he's had no such issues with his metal shed obsy conversion, so I think the option has to come back on to the table.

And in related news, my fantastic wife has been out to the garden with me to help measure up, and I now have autorisation for a 10x8 build! Nice.

[samtheeagle]

Right then, so if I'm continuing down the line of a metal shed conversion I need to think about how to provide a suitable base for it. I'm not keen on pouring loads of cement, as I'd like to keep this build as low impact as possible. My current plan is as shown in the following picture.

So what have we got here? The main supports are the 6 x 100mm fence posts, which will be fixed into the ground with these: Sabrefix Stand-Off Post Anchor Base | Screwfix.com, which themselves will be concreted into moderately sized concrete plugs sunk into the ground. Only the four corners will be full height posts, the central ones are there to support the longer beams, and so will be cut off at the same height. Around the outside of these posts I'll attach 45x75mm beams, which if the shed I get is anything like bizibilder's, will be the perfect size for the supplied metal frame to be fixed on to. The corner posts will likely need a small bit cut from them to let the metal base fit, that's what the diagonal lines represent. Then I'll put a couple of cross beams in for flooring support.

Having never made anything like this before I hope that someone can offer advice as to whether this is going to be strong enough? The longest base edge is 2.85m, but that I'm not so concerned about as it's supported in the middle by the central posts. The shorter edge however comes in at 2.26m and that's a single unsupported run. Will 47x75mm timber be able to take that kind of a span? Or should I be looking to put additional support beams in along those edges too? Is there a builder in the house!

The largest span between the beams for flooring is 95cm, so what sort of thickness / type of board material should I be looking at using? Or do I need more cross beams?

I'm also wondering about a vapour membrane too. Do I put it on top of the timber frame, sandwiched inbetween that and the metal frame? I was wondering if somehow fitting it to the underside of the timber frame might help to protect it from ground moisture, but is that required for what is going to be heavily treated wood?

I was also musing about the ground preparation. Do I build this directly over the grass and let it die off? Or should I perhaps skim the top of the turf off and pin down some of that anti-weed material to stop anything growing underneath the obsy?

Oh yes, one final thought... My biggest concern with the metal shed route is the potential for heat during the summer. I've found a silver version of the yardmaster 10x8 apex shed, I assume that's got to be better for staying cool compared to the dark green one right?

I look forward to hearing back from the brain trust

[Bizibilder]

You will need at six or seven cross beams rather than the two shown - yours are at 95cm (3ft 9in) centres which is far too wide - go for around 15-18 inches maximum between them. I would also recommend putting in at least three supports on the long sides and two on the short.

This could be starting to sound expensive!! Concrete is very much cheaper! (By the way, I had my base poured by a professional, it did cost a bit more but I didn't have to do the carrying and mixing. Concrete is heavy!)

The post anchors look very flimsy - maybe try Metpost fixings bolted to concrete pads: Metpost Bolt Down You can get them from DIY stores.

You will also need some support under the floor around (but not touching) the pier - maybe blocks or bricks - so that the floor is supported in the middle. (You don't want to make a trampoline!!).

The floor itself could be 18mm OSB (Oriented strand board) which is cheaper than plywood and is what shed manufacturers use. If the whole thing is "off the ground" then you won't need a vapour barrier - in fact you want air to circulate under the shed to keep things dry.

I would kill the grass and put down a membrane - you could cover this with coarse gravel.

Don't worry about the shed colour - it is more important to get a design with good built in ventilation, after all, you can always paint the shed!

Hope this helps.