25 replies to this topic

[Mbrisson]

I've been designing (in my mind) a micro observatory (pun intended, more to come) and slowly acquiring parts and pieces to form the dome and pier.  This past week I had some spare time to draft the autocad and model in sketchup.   

 

The design is somewhat unique as it is circular (12 segments) and employs a hinged flip top dome.  There were several reasons I ended with this approach, but I'm still not totally convinced its the best approach.  This is where I turn to fellow CNer's with observatory experience. 

 

The footprint is limited by my cap - a 6'2" fiberglass cone, repurposed from a massive microwave antenna (here's the pun!) which used to sit on a 200' high tower.  It is very light and durable for its size. at 6

' clear inside it just barely fits fracs in the 130mm f7 range which is as big as I'll ever go... using an 115EDT currenty.

 

My pier is a solid 3" steel round with a 1" thick steel base plate - this was a support leg from the same 200' communication tower!  I cut the "pier" long so I have good flexibility on overall height. A local fabricator will mill my top plate and I have an altair adapter allowing me to attach my HEQ5 - soon to be replaced by a G11G. 

 

The fg cap itself doesn't have quite enough depth therefore I plan to make the upper 1' of wall pivot with the cap.  This isn't ideal as it adds some weight and when I go to flip the lid it could become a little hard to manage. At apex, the top of the dome would be 11' in the air but shouldn't weigh more than about 40 pounds. It would flip back to the 180 degree open position, supported by pivoting legs (also used to control the cap as it moves through apex).  I could probably automate the opening using a pulley welded to the pivot axle, a belt and a drive motor however this would be down the road.  

 

Making it a roll off roof throws a lot of complexities in the mix, to the point I would scrap this plan and build a larger shed to house people and scopes.  I considered modifying the cone to create a shutter but again, it throws a lot of complexity in the mix.  I'm only looking for something large enough to house my imaging rig, with enough room for me to get inside and work on it.  

 

Concrete and fabrication costs aside I can build this out of 6 sheets of plywood and twelve 2x4's - total cost under $500.  Before I go to the extent of cutting all my wood parts I want to feel warm and fuzzy about the design.  If there's something I haven't considered, now's the time!   

 

I'm eager to hear your thoughts - constructive criticism is welcome.  

  

Clear Skies,

 

Mike

 

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[GDAstrola]

Wind load could be staggeringly high.

I am not trying to be a kill-joy.

[Overtime]

What's going to happen when the wind catches that flip-up roof?

 

Consider a roll off roof and lower the pier?

 

A flip up roof like that also keeps you from viewing in the roofs location.

Edited by Overtime, 17 March 2025 - 12:15 PM.

[bobzeq25]

A few thoughts and experiences re my similar path. There are pictures. <smile>

I tried a flip off. An obvious idea, but surprisingly difficult, which is why they're rare. One major issue is that the amount and direction of the forces involved with a simple flip off changes dramatically as the roof moves. Not an easy problem to solve (counterweights are a good idea, not easy to implement), and I eventually gave up.

The saga of that first step.

https://www.cloudyni...f/?hl= bobzeq25

https://www.cloudyni...-out-now-works/

I moved on to a roll off roof. I did not want to build the support structure, or a heavy roof, so I used structural insulated panels to build a lightweight roof, mounted on industrial heavy duty drawer slides. No other support.

That saga. <smile>

https://www.cloudyni...servatory-roof/

Edited by bobzeq25, 17 March 2025 - 12:53 PM.

[MDavid]

Rather than flip up (creating a dangerous situation) why not slide/pivot the top to one side in order to slide it open? You could fabricate a single point hinge and/or a pole from ground to top to make it work.

[TOMDEY]

I knew I had seen that geometry in some other context! --- sobering.    Tom

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[vtaDan]

I think most responders missed your comment about the top opening 180 degrees. Nonetheless, opening it without mechanization will be difficult and wind loads while opening and closing it will still be a potential problem.

In general, 6'2" diameter doesn't leave you much space inside to work if you need to do anything while the scope in mounted. Knowing me, I'd inevitably bump something.

What are you thinking for a door in the base?

[tcifani]

I've never built an observatory, but the first thing that comes to mind being an NC resident and seeing that you're in Wilmington is flooding. Maybe jack it up a foot or so on cinder blocks?

Edited by tcifani, 17 March 2025 - 02:49 PM.

[TOMDEY]

I think most responders missed your comment about the top opening 180 degrees. Nonetheless, opening it without mechanization will be difficult and wind loads while opening and closing it will still be a potential problem. In general, 6'2" diameter doesn't leave you much space inside to work if you need to do anything while the scope in mounted. Knowing me, I'd inevitably bump something.

What are you thinking for a door in the base?

@ the 90^o point wind is the hazard

@ the 180^o point there are two hazards

     1) extreme cantilevered torque at the (locked?) hinge and hinge interface to the building

     2) significant "tipping torque" on the entire building if not firmly anchored to the ground

 

Such things can of course all be addressed --- but not to be overlooked --- Holding struts, cables, winches, counter balances, springs, etc.Your observatory is small enough that it's not really a big deal... just think it through. I've dealt with these things on much bigger domes successfully. As things get bigger --- the potential energy stored or transient impulses from wind become immense, almost calling for a structural engineer to get involved or at least bless one's intuition. Even an innocent garage overhead door has a lot of stored potential energy right there --- deceptive because springs relieve nearly all of the load.    Tom

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[kathyastro]

I would think that making a shutter in the roof would be preferable to having the whole roof pop up like that.  The wind load on that open roof would be prohibitive.  It wouldn't take a lot to find yourself in the next county.

 

If you are committed to having the whole roof pop off, I would think that a quadrilateral linkage that allows the open roof to rest on the ground beside the wall would be preferable.  You would have to be creative with counterweights to make it easy to close.  But your way, you'd have to be creative with counterweights to open it, so that is a tie.

[billywjackson]

I remember seeing pictures of an observatory someone made using a large satellite dish for the roof. They cut a slot that closed with a shutter, and had it fixed to a rotating ring so that it formed a "dome" for the observatory. Something like that might also work.

Edited by billywjackson, 17 March 2025 - 08:49 PM.

[speedster]

So far, I think all commenters have been tactfully and respectfully guarded in their comments.  You might want to read between the lines and look at other solutions.  As a complete assembly, this is significantly more difficult than a ROR in every individual system from framing to waterproofing and automation could be a real deal killer.  You might want to approach this as a design project and completely abandon your preconceptions for a moment.  No cone or cylinder for the moment.  Then, without drawing anything, list your design objectives and requirements.  Then draw something that satisfies your design brief.  I suspect it won't have a cone or cylindrical shape.

 

Cylinder shapes can really cut your horizon north-south near the celestial poles.  It can also create collision opportunities since you are placing a system with roughly rectangular space requirements into a circle.  The good thing is that it is easy to set up and make measurements for design.

 

If you wind up with a ROR, there is a free online calculator at https://telescopepie...ier-calculator/

 

You might think about your pier.  6" pipe is 9x stiffer than a 3" solid round.

[Mbrisson]

Thanks everyone for the comments, I've enjoyed reading them.   I could have been more clear on the fact that the roof would not park at 90 degrees, it would rotate very close to 180, so the plate is horizontal and supported by a catch post with tie downs for wind.  Also, I plan to use a 6" W x 60"L stainless steel continuous hinge for the pivot point, it can handle the shear and lateral loads of the roof going thru its range of motion. Structure would sit on an isolated (from the pier footer) slab on grade and be achored using cast in place j-hooks - just like current residential building codes.  Clasps and gasketing for when its closed.  One of the side panels will have an inset door with gasketing.   

 

A flip top design certainly challenges the norm, and probably for good reason.  I feel like, in a small format with a lightweight dome, it may be feasible however I'm still on the fence about committing. Although I only plan to use it for AP I would like it to be a little bigger, so 20 years from now I can fit that massive SVX180!  

 

The idea of cutting in a shutter and automating the upper ring has crossed my mind several times, I just don't know enough about the automation systems and my focus is keeping it brutally simple, while also well under $1,000.   The thought of flipping a lid, turning on power/asi air or pc  and popping off a dust cap is what I have in mind. 

 

I could see building a full-blown 12x12 ROR but not anytime in the next 5 years whereas I could get the micro cone thingy up and running this spring/summer.  

 

Anywho, feel free to keep the comments rolling.  I'm in no hurry to build, and enjoy the architecture/engineering aspect of it all. 

Edited by Mbrisson, 17 March 2025 - 09:52 PM.

[Mbrisson]

I remember seeing pictures of an observatory someone made using a large satellite dish for the roof. They cut a slot that closed with a shutter, and had it fixed to a rotating ring so that it formed a "dome" for the observatory. Something like that might also work.

 

I remember seeing pictures of an observatory someone made using a large satellite dish for the roof. They cut a slot that closed with a shutter, and had it fixed to a rotating ring so that it formed a "dome" for the observatory. Something like that might also work.

I've toyed with this idea several times, but then it requires automation and fiberglass work for what is ultimately a little 6' dome.   Not that those are bad things, they aren't and I can actually do fiberglass work quite well.  Keeping this one on the idea board!

 

I would think that making a shutter in the roof would be preferable to having the whole roof pop up like that.  The wind load on that open roof would be prohibitive.  It wouldn't take a lot to find yourself in the next county.

 

If you are committed to having the whole roof pop off, I would think that a quadrilateral linkage that allows the open roof to rest on the ground beside the wall would be preferable.  You would have to be creative with counterweights to make it easy to close.  But your way, you'd have to be creative with counterweights to open it, so that is a tie.

Similar to above - and the roof would open 180, not 90 degrees as in my first photo, I didn't make that very clear.   Quadrilateral linkage... I'm imagining something like a murphy bed hinge?   I have considered mounting pivot struts above the dome's center of gravity, with lower pivot point being offset so that it  more or less swings up and over at the same time.  So much to think about!

[Mbrisson]

So far, I think all commenters have been tactfully and respectfully guarded in their comments.  You might want to read between the lines and look at other solutions.  As a complete assembly, this is significantly more difficult than a ROR in every individual system from framing to waterproofing and automation could be a real deal killer.  You might want to approach this as a design project and completely abandon your preconceptions for a moment.  No cone or cylinder for the moment.  Then, without drawing anything, list your design objectives and requirements.  Then draw something that satisfies your design brief.  I suspect it won't have a cone or cylindrical shape.

 

Cylinder shapes can really cut your horizon north-south near the celestial poles.  It can also create collision opportunities since you are placing a system with roughly rectangular space requirements into a circle.  The good thing is that it is easy to set up and make measurements for design.

 

If you wind up with a ROR, there is a free online calculator at https://telescopepie...ier-calculator/

 

You might think about your pier.  6" pipe is 9x stiffer than a 3" solid round.

I appreciate your honesty, and insight.  A large part of why I posted was to confirm/deny some of my concerns with the flip off cone concept.  I understand the constraints of a rectangular system in a circular space and had to check clearance closely in the 3d model however, with the upper 1' of wall coming off with the roof I struggle to see how it could limit the horizon... can you elaborate? 

 

Most importantly, I want whatever gets built to be functional for a long time and accommodate larger scopes down the road.   I do find myself leaning more towards a RoR box at this point.  I struggle to find confidence in the split ROR design's ability to keep water out at the centerline where roofs meet - right above the scope.  Perhaps some details of how to flash would help. 

 

The pier... I intended to weld 3-4 gusset plates from bottom to top plate and along the round to help stiffen but there is no doubt a cylindrical pier is inherently stiffer.  I actually have two 6" steel columns with flanges welded to the bottom and hot-dipped galv. they're about 10' long, so I'll cut down and fab. a top plate.  I'm moving to using one of those - they came from the communications tower!

[Mbrisson]

I knew I had seen that geometry in some other context! --- sobering.    Tom

Haha Tom. But you forgot to consider attaching a few weights below the center of gravity so at least it'll land like a parachute!   Living at the coast and working in the commercial construction and design industry, I'm all too familiar with wind loads. 

 

On the contrary, in the closed position wind uplift should be relatively minimal and due to having a solid roof part of why I'm even considering something so atypical is for weather protection.

 

I should've put a pic of it at 180 degrees open, with all the support mechanisms drawn like they are in my mind.  Regardless, I got a good laugh from your drawing. 

 

Mike

[Mbrisson]

Rather than flip up (creating a dangerous situation) why not slide/pivot the top to one side in order to slide it open? You could fabricate a single point hinge and/or a pole from ground to top to make it work.

You may be on to something here - similar to the quadrilateral hinge comment.   

 

IF I were absolutely against employing a shutter and automation I think this idea would have some merit.      I'm thinking large drawer slides for the roof to slide on, just like a ROR except there would be a fulcrum somewhere near the mid-point of the slide.   I could slide the roof back, then drop the extended edge to the ground leaving it very close to the 90 degree position.  

 

Because I have limited view of the horizon to the North it could slide that way and not affect my view. Hmmm. 

Edited by Mbrisson, 18 March 2025 - 08:05 AM.

[TOMDEY]

Haha Tom. But you forgot to consider attaching a few weights below the center of gravity so at least it'll land like a parachute!   Living at the coast and working in the commercial construction and design industry, I'm all too familiar with wind loads. 

 

On the contrary, in the closed position wind uplift should be relatively minimal and due to having a solid roof part of why I'm even considering something so atypical is for weather protection.

 

I should've put a pic of it at 180 degrees open, with all the support mechanisms drawn like they are in my mind.  Regardless, I got a good laugh from your drawing. 

 

Mike

Very good! --- and (unlike a dome) because it doesn't have to rotate and is small... it's really a pretty straight-forward concept. Should perform well with no need for fancy upkeep or maintenance.    Tom

[gordtulloch]

Thanks everyone for the comments, I've enjoyed reading them.   I could have been more clear on the fact that the roof would not park at 90 degrees, it would rotate very close to 180, so the plate is horizontal and supported by a catch post with tie downs for wind. 

Considering how much problem I had with just a gable that folded down to 180 degrees up again, I'll join the chorus urging you to reconsider this design!

 

Similarly a square building with a runoff roof is extremely simple to build, and the corners offer storage space to put all that junk those precious astro-assets you've probably got in the house or garage Future automation of a runoff roof is fairly trivial compared to the flipoff model.

 

If you insist on continuing down this path, I wish you good fortune.

[vtaDan]

You may be on to something here - similar to the quadrilateral hinge comment.   

 

IF I were absolutely against employing a shutter and automation I think this idea would have some merit.      I'm thinking large drawer slides for the roof to slide on, just like a ROR except there would be a fulcrum somewhere near the mid-point of the slide.   I could slide the roof back, then drop the extended edge to the ground leaving it very close to the 90 degree position.  

 

Because I have limited view of the horizon to the North it could slide that way and not affect my view. Hmmm. 

I like this idea. It may go against your goal of simplicity but you could use a garage door spring/pully setup to help move the roof on the slides. And counterweights and damper struts to assist with the hinge movement.  If you get all that balanced properly, you could make it very easy to open and close. 

[bobzeq25]

I struggle to find confidence in the split ROR design's ability to keep water out at the centerline where roofs meet - right above the scope.  Perhaps some details of how to flash would help.

Please note the caveat here.

WARNING - This structure was constructed by someone with no building credentials (obvious from the appearance <smile>). Or engineering analysis or even drawings. Attempting to copy it is dangerous. I don't know you well, I disclaim any responsibility for your construction. Of anything.

What you're overestimating, what you're underestimating.

Overestimating. Just how dry the inside needs to be kept. You realize that telescopes/mounts/cameras (even) are out in the pouring rain sometimes? A few drops will not do much.

With that in mind, look at the second pic here, and how I did the "flashing", Look at the left roof segment, see the dark strip on the center edge. That was a leftover piece of rooftop aluminum sheet, it overlapped the other roof by maybe 3-4 inches. There was no seal, although the flexible lip did slide some on the other roof. It kept things dry enough for 5 years.

https://www.cloudyni...servatory-roof/

The scope was offset, not to take it out of harms way (although I'm sure that helped), but to maximize sky coverage, given things like trees, and to give access to everything in the small garden shed.

Colorado is pretty dry, but we did get major thunderstorms with high winds, and the roof was often covered in snow, at times 6-12 inches.

Underestimating. The forces involved in a flip top. A LOT of leverage is involved. I started with the idea of flipping four 10 pound panels that were the plastic garden shed roof. The first time I opened one, it was pretty easy to start. At 90 degrees, there was very little force. I went a bit past 90. And the rope to the roof was instantaneously ripped out of my hands, The roof panel flew open, and tore my marine hatch hinge right off the shed on its way to the ground.

I eventually got it to work by limiting the travel to 45 degrees each side of vertical. But opening/closing was always an adventure. I contemplated counterweights/linkage, but never even tried. They'd have to be GOOD.

The split rolloff roofs I could open/close with one finger. Really. Note that the roof panels were lightweight structural insulated panels (a form of torsion box), maybe 50 pounds each. SIPs are a robust concept. They were supported by two triangles of 1X4s at each end, which transmitted the vertical load to the slides. All was attached with an adequate (large) number of VERY high end construction screws. The 1X4s could only bend if the SIPs did. Bending a SIP is not easy.

WARNING - This structure was constructed by someone with no building credentials (obvious from the appearance <smile>). Or engineering analysis or even drawings. Attempting to copy it is dangerous. I don't know you well, I disclaim any responsibility for your construction. Of anything.

Edited by bobzeq25, 20 March 2025 - 01:45 AM.

[speedster]

Water on the scope can be fixed but water on the mount electronics, computer, hub, router, and electrical connections can be a problem.  The joint between two roof halves is quite easy to waterproof.  A lip on one half, an over-riding flashing on the other, and a closed cell foam strip between the two halves.  Splitting the roof can get the halves small enough and light enough to use slides like Bob's which can work very well and both halves can be automated with one motor and one controller made for single roofs.  Lot's of positives to slides.

 

 

[t-ara-fan]

The 3" solid pier is very thin.

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[vtaDan]

 

slides 1sm.jpg

 

Is that enclosure repurposed from some other use or specifically designed? Where do I get one?!

[speedster]

Howdy Dan!  Since we are vendors, I want to respect the forum rules and moderators and not discuss offers or sales in the forum.  Pics were posted as an example of slides being effective for moving a roof.  You will need to PM me for details.