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Gingercat's Roll Off Roof Observatory

chrisblaylock

By chrisblaylock
in DIY Observatories

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chrisblaylock

chrisblaylock

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My telescope barely gets used these days - cloudy Lancashire skies and cold nights don't really motivate me to go through the hassle of dragging all the kit out into the garden, setting up and aligning it all, just for a brief spot of use before e.g. last time out my focuser battery went flat :(.   The only way to get me using the scope is to have a permanent setup.  I've read dozens of threads on here and elsewhere to weigh up the merits of different approaches, and have decided to go with a roll-off roof design, hopefully with a slight twise.  I had considered using a hinged roof, but decided against that largely due to the position of our satellite dish relative to the observatory, and generally because that would involve a degree more manual labour opening it up.  I'm really limited for space, and will be going with a 1.8m x 1.7m shed built from scratch.

The shed is loosely based on the design (and excellent vidoes) from here: http://www.house-improvements.com/shed

I'm hoping to use telescopic rails for the roof mechanism, removing the need for external supports, and generally helping the shed look more like a normal shed (it is adjacent to a (seldom used) public footpath).  Slides I'm planning on using https://www.gsf-promounts.com/tr7619-loc-front-release-locking-system-300kg-kg-pair/  The back wall would remain fixed, with just the front and 1.5m of roof actually sliding off.  How to weather proof the join is TBD.  The wind (and rain) will hit the back (west facing) wall with some force round here.

I've been having a play in Google Sketchup to get an idea of what timber I'll need, and to decide on dimensions for things.  The main concern at the moment is the height of the walls, my Southern horizon (down and left in the screenshot) looks up a hill with an 8 degree incline.  I'd like to be able to skirt the top of that hill for winter viewing of the moon, and potentially the winter sun if I ever get a solar scope.  This does however mean the scope pivot can only be ~12cm lower than the top of the shed wall, which would lead to a rather tall pier.  I'm thinking I might roll off the roof and ~1 foot of wall too, which stops the pier needing to be so high, but I then need to be careful to keep the weight down if I want to go with using telescopic rails.

The only bit I know the dimensions for thus far is the base, shown very roughly laid out below, prior to me having fun with a nail gun.  N.B. that isn't where it is going to live.  I'm holding off ordering timber for the other bits until I've decided how I'm going to proceed.

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Shed2.PNG

Shed3.PNG

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mikeDnight

mikeDnight

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I too live I cloudy Lancashire Chris and I think your decision to build a observatory is a wise one, despite your limited space. I live in Burnley which it seems is continually cloud covered, however, having an observatory close to my house has greatly increased my observing time. It also offers protection from that biting winter breeze, which is a killer, as well as offering shielding from stray light. As I use a refractor I built my walls 6'6" high which offers great protection from the elements even though it has a run off roof. 

I'm sure it will boost your enjoyment! :icon_biggrin:

Mike

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michaelmorris

michaelmorris

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It looks like a nice little project.  I've never thought of having a slide out roof.  I guess the front wall is going to have to be pretty rigid as this is the 'pivot' point of the system and you'll have to anchor down the far wall pretty well too as this could be under quite a lot of strain with the roof open.

Have you thought of raising the platform a bit so that the flank wall of your house doesn't provide such a large obstruction?

Best of luck with this interesting project.

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chrisblaylock

chrisblaylock

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Thanks for the words of encouragement chaps - it is quite a daunting, but exciting project to get stared on.

The problem with the site is it is squeezed in by the boundary wall at the back (to the south) - the ground level is 20" higher on the other side of that wall, but it doesn't actually limit the view atall.  The garage (to the north) pretty much obliterates any chance of looking north, but then there isn't much need to.  The property boundary to the west blocks a lot of the view in that direction, there's also a large tree about 20m further in that direction.  I'm well within 2m of the boundary so am height restricted to 2.5m in total from ground level, so if I start raising the platform even more (it is currently at 25cm above ground level), I'll be forever bumping my head inside (I'm 6'2").  The big trade-off is headroom vs how close to the southern horizon I can point.

I'm just glad it is going ahead, the second I'd cleared out behind the garage (which involved digging about half of it out that was an earth bank), the wife said "oooh, that'd be a good spot to stick the inflatable hot tub"!  NO!

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mikeDnight

mikeDnight

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Hi Chris, although its always nice to get as close to the true horizon as possible, you may take comfort, as I did, that most things within 30 degrees from the horizon are rarely worth looking at due to turbulence and depth of atmosphere. For that reason I set my pier height so that the scope did not sit too high and get troubled by wind and stray light from surrounding street lighting. Quality rather than quantity! :happy11:

I've attached some pics to give you an idea of the self imposed horizon created by my observatory walls, and one with the roof closed to show how close to the roof the scope is mounted. 

Mike

 

 

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2016-12-07 13.06.05.jpg

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chrisblaylock

chrisblaylock

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Thanks Mike - looks pretty cozy in there!  I also like the cunning use of the exercisemat edging as a shelf guard :)  Good point about the extra protection from breezes offered by a higher wall.  Once I've got the base up, I can mock up some walls with cardboard and double check the viewing angles with the scope on a tripod to get a feel for the best wall/mount height.

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chrisblaylock

chrisblaylock

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Roof slides ordered - went with these in the end https://www.gsf-promounts.com/container-red-slide-non-locking-medium-duty-hi-load-180-250-kg-pair-pair-pricing/

They'll extend just over 1500mm and take 200kg, so that should be plenty for my needs.  Ideally I'd have liked 1700mm ones, but they cost more than twice as much.

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chrisblaylock

chrisblaylock

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Base now in situ. A load of timber coming tomorrow to build the rest of the frame. It is going to be a tight squeeze. Currently deciding on cladding - will probably go with coated steel given it will be impossible to access once built. There's also the issue of how to avoid the gutter on the back of the garage, may reduce wall height and increase pitch of roof.

20170607_131635.jpg

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chrisblaylock

chrisblaylock

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I'm planning on sticking some insulation panels on the inside, but it will only be the roof that'll get hit by the sun once the hedge has grown up.  Don't get too much sun round these parts anyway ;)
Hoping to get the roof on this weekend, but the weather doesn't look great and I'm booked in to help neighbours digging trenches for gigabit fibre broadband (B4RN) tomorrow.  Fingers crossed anyway!

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darknight

darknight

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i take it that the condensation that the metal sheds have will be taken care of with the membrane side wrap? wall timbers what size have you used?, I'm looking forward to seeing those sliders working as ill probably use them on my build later this year, nice job so far mate.

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Mick J

Mick J

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That looks fantastic Chris, unfortunately I would like to see a video if you please, have to do these things properly :icon_biggrin::icon_biggrin:

Are you worried regarding the roof spreading ?  would a brace between the two 3x2's or a triangle of ply - perhaps you feel it's strong enough and I am being silly, great work with the runners. 

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