View Full Version here: : Roll off Roof Observatory Design
18-04-2008, 02:07 PM
Due to factors beyond anyones control I am not now buying a SkyShedPOD. I have built the deck and it is 3.5m x 3.5 m. Below are some drawings of the current concept. The frame will be pine and lined with 5mm ply. The outside will be clad with cedar wb's with sisalation and pink batts in the walls and roof cavities. The wall is only 900mm high when open and the highest point inside is about 2.7m. Inside it will be 3.3m wide and 3.0m deep.
Here are a couple of drawings of the 'roof' closed and open.
Any further ideas or comments?
18-04-2008, 02:38 PM
Interesting design, Bert.
Any particular reason to go so low with the side walls? You're obviously not worried about wind.
The roof has potential to be very flexible at the end that separates from the fixed wall, since you won't be able to brace/truss that end much and still have it clear the pier. It can be done, I know, but you'll need to pay attention to that.
18-04-2008, 08:41 PM
Hi Bert, I've wrestled with something similar as I try to develop my own observatory which already has non-negotiable pre-existing elements to its design/construction. My solution is certainly not a suggestion for you, but within my deliberations/designing there may be a "spark" for you to strike on.
My deck/platform was something I had already built, free-standing and elevated above my backyard olive grove at approx 4 metres, a very small job measuring 2.5 x 2.5 metres free-space.
After several working designs I decided that having the mount permanently set-up on my pier was the most important issue; so that only having to place the scope (with dovetail bar and rings affixed) onto it and doing some minor drift aligning would see me ready for action. This whole situation would be expedited by having the scope in an insulated weatherproof container at the side that will double as a bench seat and storage space for other equipment.
Fabricating an aluminium bracket that is affixed to the pier some distance down from the levelling plate that accomodates 2 halves of a "collar base," allows me to create a weatherproof box or container that slips down over the mount assembly and is lever-locked into position for protection during of non-use.
Later on I may fabricate a larger "cockle-shell" container from fibreglass that could hold the scope et al and have the advantage of being stream-lined - somewhat similar containers are, I believe, used to stow equipment on ships' decks etc.
None of the above is particularly relevant to you Bert (although it may be to others) but along the way to this final design I canvassed others that may be in some way.
Seeing that your fixed walls are so low (900mm) I presume that you are not envisaging this "shed" as a shelter for yourself etc: and I can only presume that there is an element of concern about winds to make you opt for this particular design/dimensions. Or perhaps it is a specific aesthetic you are aiming for?
Having said that you could easily raise the height of these 900mm walls and not need such a height for the roof to clear the pier and scope set-up etc, employing a lower profile roof.
Another point worth making is that dispensing with the fixed wall at one end as per your diagrams, and making that end an opening (2 door?) end to the whole unit would give you the ability to re-close these doors once you had opened up the observatory and thus returning the structural integrity to such a design that would be (possibly) suspect without "walls/structures" at both ends.
All this may well be "tripe" to you Bert, but as I said, something in it may have some merit for you to consider!
Best of luck with you constructions, Darryl.
18-04-2008, 08:48 PM
That looks OK for a start, heres my OBs for wall/roof ideas, (about the same size). I assume the pier is isolated from the floor.
On relection, after my build, a flat roof is easier, so long as it clears the scope in any orientation, that is critical if you want to close in a hurry (ie if you leave it open all night and it suddenly rains). As al says, low side walls sound sexy for low angle imaging, but really, atmosherics are **** near the horison , and wind can be a bother.
Withe so much insulation, you may find you have to allow an hr or so for cool down before imaging too. (why the insolation BTW?.)
21-04-2008, 11:34 AM
Thanks for all the replies. I put this up to sound out the combined wisdom at IIS in case I missed any major design consideration.
The reason for having the wall so low is so I can easily carry OTA's etc in without negotiating a narrow doorway. It is the twisting when carrying a load that literally screws your back. Mine is fine and I want to keep it that way. The south wall without the door could be higher but I like the symmetry. Wind is not a problem at my place as the whole of my backyard has trees that shelter it from all but the strongest winds 20+ knots.
The open end will be adequately braced with ply at the corners. A flat roof that clears everything would make the sides too high. I may put another door in the high wall for easy access when closed.
I have been in enough tin sheds in summer to know that insulation is a must against radiant heat. There will be heaps of ventilation through the open deck floor as well as under the eaves of the roll off roof. A couple of 12" exhaust fans one at each apex of the ends should get any hot air out. Any potential condensation build up in winter should also be stopped by adequate ventilation.
I sit inside when collecting data as my main computers are wirelessly connected to the laptops that control the autoguiding of the mount and the camera. I really only go out to focus and aquire the target. I also am of the old school and need to see as much of the sky as possible to find my way around manually. That is I do not use GOTO. I reset each exposure set manually as I watch them as they come in. I only have a nap if there is no chance of rain by keeping an eye on BOM radar. You can still get caught in Melbourne.
As I am retired when I image I am up all night till dawn and It would be nice to just shut the roof and go to sleep. Having the walls low also means that it is far easier to pull the roof shut without having to reach above about waist height.
21-04-2008, 06:41 PM
My 6m x 3m run-off roof observatory had framed walls 1.5m high, AC sheeting, with a skeleton rib framed roof, two parts to bring the hight up to 2.7m
The door in the south side was access etc.
I went on an overseas trip during construction, when I got back...... enough said!!!
21-04-2008, 07:32 PM
LOL, I can see a hobbled, broken man in that 2nd pick :D
21-04-2008, 08:49 PM
I was actually looking for the main mirror from the scope..... had to be here somewhere!!!!!!!!!!!!!!!!!!!!!!!
22-04-2008, 01:02 AM
Looks like a great spot for an "observatory" , a lot nothing around it.
Who said an observatory shed has to be pretty or look professionally built ?
22-04-2008, 01:05 AM
mmmm ..... not a good start , loosing your primary under all the rubble ....
22-04-2008, 10:44 AM
True Ian, but I reckon Merlin would want to add "but it has to be structually sound!"
Despite my humour Merlin, you have my (retrospective) sympathies for that unfortunate trauma of the past - and I know that the image of you was not that of "a hobbled, broken man" as Fred suggested: nor were you really looking for the primary mirror - you were actually looking for the door key so you could get inside the wreck!
22-04-2008, 03:39 PM
What a spot for an observatory!! The winds can cause lots of grief BUT the views.
22-04-2008, 03:47 PM
The observatory was set up on my block at Tooborac, Vic.
The site was so good, that in the early 90's the ASV photographic group used to come up and observe as a "Dark Site".
It was instrumental in Leon purchasing the 40 acres, just North of Heathcote, as a "Dark Sky Site"; he transferred ( God bless him!) it to the ASV and it's now the LMDSS.
No power, water etc, but as you say ..... what a site!!!
22-04-2008, 05:00 PM
Ouch! Merlin66. I really feel for your loss due to the wind damage.
We just had very high winds in Melbourne and apart from a bit of turbulence around the deck I think a tent would have survived due to the shielding effects of the trees. The tarp I had over the mount barely moved!
It just shows every site is unique and all variables have to be considered.
22-04-2008, 06:46 PM
mine stood up to the high winds we recently had no problems... i built 5 inch posts to the cieling as we are very exposed here. ( i note yours is more protected bert)
i chose timber for the walls with pleny of natural ventilation, it never gets hotter than outside and cools down quickly the walls dont hold the heat either.
just a couple ideas ... though i think whatever you do will be done well.
12-05-2008, 02:43 PM
would work a charm
heres what I did in the mid west vic.
13-05-2008, 03:05 PM
Hi Bert, Merlin66 (Hi Ken!) said "structurally sound". Now as the name of your street suggests, bolt the whole lot down otherwise your obs will be joining his old one in Toobarac. You know how fickle the weather can be here in Vic, sunny one day cyclone the next! Isn't the idea of an observatory supposed to obviate the requirement of disassembling your scope all the time?
13-05-2008, 05:06 PM
Roger and the guys,
The shutters although ripped to pieces didn't move from the tracks. I used 6 x3 C lipped channel purlins, with 5 1/2" nylon rollers, so they could not lift/ move out of the guide. Each shutter was 3m x 3m and could easily be moved by hand.
The basic design was good, just I didn't have the time to finish the sheeting before heading of to Thailand. Would I build the same again???? If I still had the 18" scope to house, Probably.
13-05-2008, 05:56 PM
I have changed my mind and I am going to build a conventional gable roof design with the two gables running off to both sides. The walls will be 1.6-1.7m tall. The apex of the gable will have lots of ventilation. It will all be done in wood to minimise radiant heating of optics. I promise to bolt it down Roger.
I am currently testing and adjusting a focal reducer/field flattener setup for a Meade SN10 for a full frame camera. Would you believe f/3.4_3.6! and flat field with almost minimal vignetting. So far looks very promising.
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