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  #41  
Old 22-09-2010, 12:34 PM
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SMan (Henryk)
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You need to publish that in "Better Homes and Observatories" or something...that is just stunning.
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  #42  
Old 22-09-2010, 08:26 PM
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Thanks Henryk and others for the positive feedback. The only thing missing recently has been a clear sky. As for publishing an article, the thought had crossed my mind - maybe something for the IIS projects department.

I'm still considering motorising the dome and will be aiming for a low-profile non-clunky solution.

Chris
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  #43  
Old 30-10-2010, 05:20 PM
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Dome construction pics

Seeing Robin's latest pics prompted me to dig out a few dome construction pics, which I had omitted to include in this thread.

Basic details: I used the Desert Domes Calculator with 3V "fineness" and a 3.6 metre diameter. http://www.desertdomes.com/domecalc.html
The geodesic dome uses 105 triangles from 9 mm exterior ply. Edges were beveled by hand plane and joined with liquid nails and plywood hubs (to suit the pentagonal or hexagonal shapes) fixed by screws.

As others have found, it's easier to start construction upside down. Due to the weight and size, I turned it up the right way before it got too big and heavy. The finished weight was about 90 kg although this increased to around 220 kg once the dome ring and steel turntable ring were added.

All joints were sealed with ample Sikaflex and painted externally with a very thick Solagard. The inside was painted with a mould-resistant black paint.

Chris
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  #44  
Old 30-10-2010, 05:36 PM
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More dome pics

A few more pics.

I projected a vertical laser line to mark out the cut lines for the aperture. Something like 2 days to mark it out and 20 minutes to do the cut!

The shutter (Mk II) comprises two curved plywood side pieces, spaced apart by three lengths of 10 mm threaded rod. I fixed 35 mm bearings to each end of each rod; these ride on aluminium strips fixed to the top of the aperture frame. The tracks are extended beyond the frame using 6 mm threaded rod as standoffs. This was a bit fiddly but it works well. I first tried thin plywood sheet as the shutter surface, but the join was unsuccessful. The final version uses 0.55 mm sign-white sheet metal. Since a full-length shutter can't be parked, the lower 0.5 m of the aperture is covered by a hinged shutter that doesn't normally need to be opened.

Chris
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  #45  
Old 05-11-2010, 07:01 AM
issdaol (Phil)
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Beautiful setup mate
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  #46  
Old 16-04-2011, 05:40 PM
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A late afternoon pic today shows the sheet metal weather seal, and the aluminium shutter tracks. Fabrication of the weather seal was complicated because I forgot to make the diameter of the walls a little less than that of the dome. Therefore, the seal, which is attached to the dome, needed a step so that it would clear the walls. Truth be known, it could have done with a larger step as it binds occasionally - depending on the temperature.

Chris
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  #47  
Old 16-04-2011, 09:05 PM
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Quote:
Originally Posted by ChrisM View Post
A late afternoon pic today shows the sheet metal weather seal, and the aluminium shutter tracks. Fabrication of the weather seal was complicated because I forgot to make the diameter of the walls a little less than that of the dome. Therefore, the seal, which is attached to the dome, needed a step so that it would clear the walls. Truth be known, it could have done with a larger step as it binds occasionally - depending on the temperature.

Chris
very picturesque - you could try a silicone spray to keep it moving smoothly - i use some on my dome
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  #48  
Old 16-04-2011, 09:44 PM
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Now that is a good idea. Thanks David. I'll have to give it a try.

Chris
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  #49  
Old 10-06-2011, 09:35 PM
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Originally Posted by h0ughy View Post
very picturesque - you could try a silicone spray to keep it moving smoothly - i use some on my dome
I eventually tried the silicone spray today, and it has worked a treat! Much smoother and quieter running. Thanks h0ughy.
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  #50  
Old 18-06-2011, 05:23 PM
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and joined with liquid nails and plywood hubs (to suit the pentagonal or hexagonal shapes) fixed by screws.
Hey Chris, can I ask, did you get this idea from my dome or did you see it elsewhere?

As far as I know, I came up with this original idea when I built ASIGN and couldn't afford the usual strips I had seen others use to join the triangles. Once the inspiration for the little pentagons and hexagons was realised and worked, I was happy for the whole world to use it. I've since seen them used on other observatories and it would be personally interesting to find out where people get the idea from.

Baz.
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  #51  
Old 20-06-2011, 09:39 PM
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Originally Posted by bloodhound31 View Post
Hey Chris, can I ask, did you get this idea from my dome or did you see it elsewhere?


Baz.
Baz, I suspect that you're right: I probably did get the idea from you. I can recall looking over your construction notes pretty carefully on your website, as well as those from Barry Neumann (who fibre-glassed cardboard) for his geodesic dome. Either way, the idea worked well. Originally, I overlooked liquid nails and tried ordinary wood glue, but that was hopeless. The final result was very strong. Tonight, it will be subject to 120 kph wind gusts here, so I've battened down the hatch even more than usual.

Cheers, Chris
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  #52  
Old 20-06-2011, 10:34 PM
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Originally Posted by ChrisM View Post
Baz, I suspect that you're right: I probably did get the idea from you. I can recall looking over your construction notes pretty carefully on your website, as well as those from Barry Neumann (who fibre-glassed cardboard) for his geodesic dome. Either way, the idea worked well. Originally, I overlooked liquid nails and tried ordinary wood glue, but that was hopeless. The final result was very strong. Tonight, it will be subject to 120 kph wind gusts here, so I've battened down the hatch even more than usual.

Cheers, Chris
Thanks Chris, it's just interesting is all. I would like to see the idea spread as my little "Thank you" contribution to the world for all the help I got from others when I built mine.
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  #53  
Old 16-07-2011, 05:21 PM
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Cleaning the dome

After more than 3 years in place, the pristine white dome was no more. Especially on the Southern side, it had turned a grungy green, although from a distance, the overall impression was still white.

Today I sponged on some sodium hypochlorite in the form of "30 second Outdoor Cleaner" that I got from the local hardware. A rinse with the hose then revealed the pristine white again.

Because my dome is over 5 metres tall, I can't quite reach all of it from the ladder or from the slot, so the plan is to put a sponge on a stick to complete the job. Anyway, the photo shows you how well it is working!

Chris
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  #54  
Old 17-07-2011, 12:19 AM
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Whoa! SHINY!
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  #55  
Old 24-07-2011, 11:08 PM
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Chris, can you please tell us a bit about how you worked out the curve of the stairs, and how you attached the steps themselves to the wall?

I assume the curved bit is roll-formed flat steel? What do I need to know to make a set of stairs like this? My internal wall diameter will be a little under 5 metres and ascending 2 metres to the floor above.

Any help would be appreciated.

Baz.
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  #56  
Old 25-07-2011, 11:02 PM
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Stair design

Baz, The stairs are generally (see below) 600 mm wide and rise 2.35 metres, with a total of 12 steps including the landing. The key component was the 200 x 10 mm plate that I had rolled to a helix with a radius of 600 mm less than my observatory radius (inner wall). From memory, this was pretty close to a radius of 1100 mm. Of course, the helix has to rise the distance that the stairs do. (So for your obs, if the inside radius of the wall is say 2400, and you want stairs 600 wide, then the helix would have a radius of 1800.)

The sketch that I presented to the rolling shop showed a cylinder of 1090 mm radius, with a band (forming the helix shape) rising from the ground up to the top of the cylinder over a specified portion of the circumference. I've attached the sketch that I gave to the rolling shop.

As it turned out, they rolled it for the wrong hand (ie. did not follow my drawing), and they had to do a fresh one for me. They also had trouble keeping a constant radius, with the result that my stairs reach a minimum width of 545 mm about 3 steps from the top, but they flair out to 800 mm wide at the bottom. At first this seems to be not good, but in reality, the flair is perfect. It gives the stairs a more grand appearance!

The steps are solid hardwood (Vic Ash) 25 x 160 mm. On the stringer, I bolted a 50 x 50 mm angle for each step, and secured the step with a couple of wood screws to each one (from underneath). The outer end of each step rests on a pine batten which is itself screwed to the stud frame.

I welded a flange to the top of the stringer and it's bolted to one of the floor joists (190 x 45 F17). The bottom of the stringer is bolted to the concrete slab with a small bracket. The whole result is very solid.

Some quick pics attached.

Hope that is of some help.

Chris
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Last edited by ChrisM; 26-07-2011 at 09:38 PM. Reason: Added more pics
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  #57  
Old 26-07-2011, 10:20 PM
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AH YES!! I see it now. You have answered one of my toughest questions in one photograph. I was wondering about the helical roll on the 10 x 200. You wouldn't believe it, but I found a piece that might match exactly, sitting out the back of my old place of employment. I've hit the boss up for it.

Of all the features of an observatory, I like your spiral stair the most. I've GOTTA have one!!

Now all I have to do is work out what measurements to give the roll-formers for my 2.5 radius room with a 2 metre high wall.......maths has never been a strong point beyond simple arithmetic for me.....

Thanks so much for the advice mate.

Baz.
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  #58  
Old 01-08-2011, 06:30 PM
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I've visited this thread many many times, and I am always amazed at how brilliant your observatory is Chris. I can only dream of having my own like that one day.

Well done!
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  #59  
Old 02-08-2011, 06:56 PM
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Quote:
I've visited this thread many many times, and I am always amazed at how brilliant your observatory is Chris. I can only dream of having my own like that one day.
Thanks HolyWars - It took a lot of thought and effort to design and construct it, but I would venture to say that anyone with a few simple building skills (and I am not a builder) and the will, could build something of which they are rightfully proud.

You have to live your dreams!

Chris
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  #60  
Old 23-10-2011, 04:40 PM
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More enhancements / upgrade

A few enhancements and an upgrade have occured over the last month.

I got some cheap digital thermometers and have put these on a panel to show concrete pier temp, steel pier temp and the ambient temp upstairs. No surprises here - the concrete pier is always lagging the trend.

Also from ebay, I got a cheap ($5.47) IR light which I use to boost the lighting for the scope/mount surveillance CCTV. Sample pic attached. The view is actually clearer than this snap would indicate. I've wired in a 5 Watt resistor into one leg of the SPDT centre-off switch to provide a Low/High lighting option.

To better protect the telescopes and mount, I got a custom-made cover made from tent fly material. The actual material is purple PU-coated nylon, and it's got a drawcord which allows me to pull it in tight around the pier. I place a few silica gel dessicant canisters around the mount to help keep any trapped moisture under control.

And last but in no way least, I've replaced the LX90 with a larger SCTand a 5" refractor, both of which sit on a 1200 GTO. It's still very early days with this set-up - the refractor hasn't even seen first light yet.

I'll post more in due course.

Chris
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