Starting to Think about a new Obs design.

[ribuck]

Hi All,

I'm moving to a new house later in the year when it's finished being built, so i'm starting to think ahead about a new observatory. I've previously built a motorized dome based obs in the past, but this time i'm looking to build something a little simpler, so have opted for a roll off roof design this time round.

Pier Design

After reading through many threads I have decided to try and keep the costs down and go with a concrete pier which i plan to use for imaging. Now my first question of this thread is about the diameter of the pier for imaging, some people say 160mm is fine others recommend 200mm+. Would a 160mm concrete / pvc based pier be stable enough for imaging with either a 102mm refractor or a 200m reflector.

Roof Design

The second part of the puzzle is the roof design, trying to understand what approaches people have taken to get a good fit / seal whilst maintaining smooth operation. Any idea's suggestions are welcome as it's sometimes hard to tell how people have approach this from some of the build threads.

Out of interest, has anyone every just bought a stock shed, and modified just the roof ?

Many thanks in advance for any help received,

Rich.

[Jessun]

What a delight to have such a project coming! When I do, IF I do, I'd get the pier as solid as I can - concrete costs next to nothing and is an absolute pain to re-do. Go big. As for roof, a look at Gina's mishap in the wind gives a few clues of what forces you may be up against that's not that apparant on a sunny day.

Good luck!

[Bizibilder]

I modded a metal shed and so for (nearly 3 years) it has worked faultlessly. Have a look at the Blog in my sig (around October 2009) for details. Hope your move to your new house goes smoothly and that the obsy build is higher on the priority list than decorating etc!!

[Carbon Brush]

May I suggest a look at other people's sheds?

I only manged to look at one before building. The owner was happy to point out the errors as well as the good bits.

My roll off has some good features, and some things I would not do again.

It is based around a stock shed with almost the same money spent again to make it suitable.

I don't think you will be knocking on my door for a shed inspection though, Newcastle is about 150 miles away. But I'm happy to send you some photos of construction details and maybe someone local will offer a 'tour'.

[Tim]

Get the house builders to build it?

[Enrico]

Certainly get the house builders to make provision for electricity out there - I.e. a conveniently placed fused spur which you can join an armored cable into once you build your observatory.

And whilst they are at it, provision for Cat5 too - cabled connections are always better than wifi. It amazes me that more buildings do not conclude structured cabling in these days. It's so cheap to do it when the building is a shell, but so hard (and therefore normally expensive) to do it once it is complete.

I'd also get them to lay the slab for an obs/shed too. Cost to them very little if they are doing concrete for all the floors etc., but would make your life a whole lot easier later on.

[ribuck]

Yeah cabling power / network etc aren't a problem. Ok people, what about the roof sliding mechanism, what are people using for rails / wheels and how have you ensured a good seal ?

[Bizibilder]

Nylon castors on wood - quiet and accurate with suitable wooden guide strips.

[ribuck]

Roger, i checked your blog and couldn't see a link to your shed mod, can you post a link to the page please.

Rich.

[Bizibilder]

It starts about here: http://bizibilder.blogspot.co.uk/2009_09_01_archive.html There is also a thread in the DIY obs section but at the time I was wary about posting pictures and so it is just a series of "look at my blog" posts .

[Astrokev]

Would a 160mm concrete / pvc based pier be stable enough for imaging with either a 102mm refractor or a 200m reflector.

Rich.

Hi Rich,

For a 200 metre reflector I think you may need something bigger than a 160mm pier.

It's a good question though. I've been struggling to know how big a pier I need for my EQ6 and 10" Newtonian. I have 2 lengths of freebie air-con ducting - 1 looks too narrow, the other too wide. Ah, decisions, decisions! Watching this thread with interest.

Kevin

[ribuck]

I think i'll probably just go with 200mm PVC pipe filled with concrete and rebar for the pier. Will probably just use cretepost as there is no mixing involved other than water.

As for the roof rail system & seals the search goes on, and will probably just be easier if I approach people directly and quiz them about their designs.

[Bizibilder]

What do you mean exactly by roof "seals"? There is some advantage in allowing air to circulate around the Obsy - especially in keeping it cool and preventing condensation.

[ribuck]

Hi Roger,

By seals, i just mean the point at which the sliding roof component meets the shed walls to ensure a water tight seal. For ventilation i will just have an air vent at each end of the shed to allow air flow. I'm probably going to approach stardust and his build looked very nice, and hopefully i will be able to quiz him about his design and any problems he encountered.

Rich.

[Gina]

My roof sides overlap the fixed walls by a couple of inches, there is no seal as such. This allows some air circulation without letting any rain in. The ends of the sides are sealed with brush type draught excluder - very effective. Where the roll off roof overlaps the warm room roof it's just that - an overlap of 2". The torrential rain and storm force winds of late have not resulted in any rain ingress It's been a severe test!

[Bizibilder]

Mine, like Gina's, just has at least 1" (or 2") overlap on three sides - no rain gets in. The "door" side - which is the one that the roof has to pass "over" to close has a thin steel "drip" (part of the original shed) that just clears the wall and passes over it by about 1/2". This is enough to prevent any water ingress and we have had our fair share of horizontal rain in Norfolk over the past year or so.

hope the sketch makes things clear:

[Astrokev]

Rich,

I can't offer help from personal experience, but I'm starting to design my own obs recently and have been pondering on how to cover the gaps between wall and ROR. Getting a perfect seal would be very difficult, if not impossible and, as others have said, there are advantages in having a small gap for air circulation. My current thinking is to keep the gap as small as possible and attach brush strip. I think this would still allow a degree of air circulation whilst keeping the worst of the weather and big beasties out of the obs.

If you browse all the buils in this section you'll find lots of designs to help you decide what works for you.

Looking forward to seeing your build...lots of piccies please!

Kevin

[Bizibilder]

Funnily enough its not the beasties that have caused me any problems! The main concern has been the week in September when two nearby Silver Birch trees deposit their seeds all over the place!! They are quite small and blow in everywhere. I cure the problem by giving the whole place a good vacuum.

[ribuck]

Hi Kevin,

I'm a long way off myself as i wont be building until june when the new house is built, so wont be able to post any pics any time soon, unless your interested in a motorized dome build which i did at my last house

[ribuck]

i'm mulling over a few idea's as we speak, so i'll probably start knocking up a few drawings in sketchup over the weekend, and at least then i will be able to properly visualize the design and iron out a few design kinks before i start any building work later in the year.

[laser_jock99]

Roof seals - parallel to the rail sides allow plenty of roof overhang. At the perpendicular ends a heavy duty rubber flap can be used to give a weather seal. I have also nailed down some brush type draught excluding strips in place to keep the 95% of residual draughts out.

This photo shows the overhang (about 1' all round), weather flap & rails.

More images of my build here if it helps?

http://s48.photobucket.com/albums/f206/laser_jock99/ASTRONOMICAL/Cambrian%20Mountains%20Observatory/?start=all

[ribuck]

Thanks laser_jock, your photo's really helped, and can i just say that i'm so very jealous of the stunning dark skies you have...............sigh.......if only......

[Enrico]

Not built an observatory myself, but was thinking could the roof "drop down" to make a seal.

I.e the castors go down a short slope at the end and the roof makes a seal (rubber seal?) with the walls. A lever would be needed to get the roof rolling though (something like a bottle jack would probably do the job).

Just an idea, as I say not (yet) built an observatory.

[ribuck]

Hi Enrico,

I'm probably just going to have a decent overhang for the roof, and where the roof meets the walls, i'll probably keep the gap down to a few mm, and then just use some brush draft guards and a strip rubber to keep out most of the moisture / debris.

Going to have a look at my local diy merchant to see what sheds they have to see if they could be easily adapted, just to save time on the build process, as I have a baby due to arrive at the same time we move house, so time to build will be limited.

I'm going to measure up and see if i can get away with a 8'x6' or 8'x'8 shed.

Rich.

[Bizibilder]

Have a look in the DIY place and buy online!!