106 replies to this topic

[cavedweller]

I am ready to break ground on the first of three planned domes. This first one will be a ten-foot Technical Innovations Home Dome. I disassembled and transported this dome from Montana last spring. It includes full automation hardware. It has been sitting in my backyard in town since then. 

 

I just moved a shed from the area where I will locate the dome. I have a limited time to get this dome done because the scope going in this dome is currently being hosted in New Mexico and is only allowed a limited time from now until I must move it.

 

The dome has a three-foot tall round wall, but I need at least five feet. I contacted the manufacturer, and they told me they are no longer building domes or dome fiberglass parts, so I need to figure out how to increase the height of what I have. Here is a picture of the site and the dome as it currently sits:

 

 

[EFT]

I don't understand that.  Of course they are still making domes unless they just shut down and haven't told anyone.  All you need are some additional dome rings for a 10' dome.

[JimTheEngineer]

Do some type of nice rock or brick wall 2ft high in a circle. Hire a mason. I think it would look really sharp and might be less cost.

Edited by JimTheEngineer, 01 April 2025 - 12:21 AM.

[cavedweller]

I’m sure I’ve got enough rocks around here, but bricks are more my style.

[cavedweller]

My first step is to create a rough plot plan. There are several factors I need to consider, the most important two being the diameter of the dome and a needed 36-in offset of the pier south from the dome center. So, starting from scratch, I determined the general area where I want this first dome. As described in my first post, I had to move a shed to put the dome where I want it, which gives the best views to the south and east. The view in the picture is actually more to the southwest; south is at the left edge.

If I stand roughly where I want the center of the dome and face the concrete, I can call the edge the x-axis. I can look over to the right and call the corner of the concrete the origin point. I want the dome front edge to be two feet from the edge of the concrete, so at x = -2, and the dome east edge (right side) one foot from the corner of the concrete, so at y = -1. This puts the center at x = -6 feet and y = -7 feet. To make things more complicated, the edge of the concrete is not east-west. If I now turn to face north, I will turn counterclockwise by about 49 degrees (according to an analysis using Google maps). This means the pier offset needs to be southeast of the dome's center. A little bit of trigonometry tells me the pier needs to be at x = -72+36*cos(49) = -48.38 inches and at y = -84-36*sin(49) = -111.7 inches from the corner of the concrete.

The approximation of the angle will be fine-tuned once I get the pier in place, and then I can make sure the center of the dome is 36 inches directly north of the pier by setting up a telescope directly over the pier and make a sightline to Polaris.

 

Here it is in a drawing:

 

[Victory Pete]

My first step is to create a rough plot plan. There are several factors I need to consider, the most important two being the diameter of the dome and a needed 36-in offset of the pier south from the dome center. So, starting from scratch, I determined the general area where I want this first dome. As described in my first post, I had to move a shed to put the dome where I want it, which gives the best views to the south and east. The view in the picture is actually more to the southwest; south is at the left edge.

If I stand roughly where I want the center of the dome and face the concrete, I can call the edge the x-axis. I can look over to the right and call the corner of the concrete the origin point. I want the dome front edge to be two feet from the edge of the concrete, so at x = -2, and the dome east edge (right side) one foot from the corner of the concrete, so at y = -1. This puts the center at x = -6 feet and y = -7 feet. To make things more complicated, the edge of the concrete is not east-west. If I now turn to face north, I will turn counterclockwise by about 49 degrees (according to an analysis using Google maps). This means the pier offset needs to be southeast of the dome's center. A little bit of trigonometry tells me the pier needs to be at x = -72+36*cos(49) = -48.38 inches and at y = -84-36*sin(49) = -111.7 inches from the corner of the concrete.

The approximation of the angle will be fine-tuned once I get the pier in place, and then I can make sure the center of the dome is 36 inches directly north of the pier by setting up a telescope directly over the pier and make a sightline to Polaris.

 

Here it is in a drawing:

 

Home Dome Ten Feet Plot Plan.jpg

Fun isn't it?

[cavedweller]

Yes. So, with one more calculation, I can locate a point on the edge of the concrete in the estimated north direction of the center of the dome (and pier), which is x = -72 - 84*tan(41) = -145.02 inches. I will verify that point using the scope and Polaris as a sanity check before I dig for the pier.

 

I am planning on a 24-inch round, 72-inch-deep concrete pier foundation flush at the top with the (isolated) surrounding 13-ft by 12-ft by 5-inch slab. I inquired with United Rental, and they quoted me $1300 for me to rent the equipment required to dig the hole (for one day). I will consider that cost when I get the quote for a contractor to do the work. If I dig the hole myself, it might be bigger, but shallower; maybe 36-inch square and 48-inches deep.

 

Updated drawing with north point indicated:

 

 

 

Edited by cavedweller, 01 April 2025 - 08:22 PM.

[Kitfox]

I must have missed it in the other thread, what scope and mount will go in here?  I'm trying to wrap my head around a 3 foot south offset in a 10 foot dome    I'm assuming a fork mount or a bent pier?  I actually wish I had done a couple of bent piers in my observatory...

[cavedweller]

Yes, a 20” Cassegrain with fork mount on a wedge.

[Kitfox]

Yes, a 20” Cassegrain with fork mount on a wedge.

 

That is not in your signature!     The Tinsley is so jealous....

Edited by Kitfox, 01 April 2025 - 10:35 PM.

[cavedweller]

Before it got dark, I did a fast mockup with a tape measure and placing rock markers. Once it was dark, I stood about where the center of the dome would be, and quickly found out that by moving everything six feet farther from the corner would allow the house to block most of the direct light from the Navy airfield, including the beacon they added only a few weeks ago. So, that's what I'll do.

 

Also, while updating the drawing, I discovered I did the last calculation correctly but labeled it wrong on the drawing.

 

This updated drawing has the new measurements and the correction:

 

[cavedweller]

That is not in your signature!     The Tinsley is so jealous....

 

It is currently in New Mexico at a hosting site. I only have a few months to move it. I just know I don't want to pay for hosting it there any longer since I am 99% a visual observer.

[Kitfox]

The dome configuration will help a lot with non-scattered light, as well.  I spent a lot of nights under the dome at UNC-CH's observatory right in the middle of downtown Chapel Hill.  The limiting visual magnitude inside the dome was significantly better than on the surrounding terraces.  The obscuration the dome provides makes a huge difference.  My ROR has 7 foot walls, but all the light domes around my Bortle 4-5 site have an impact your solution would have kept me shaded from.  Domes are sweet!

Edited by Kitfox, 01 April 2025 - 11:50 PM.

[cavedweller]

Yes, I also look forward to the little bit of wind protection the dome will provide. I will miss being able to see the entire sky while in the dome, but I undoubtedly will still roll out one of my other scopes on a calm night and have that, too.

[cavedweller]

Being too windy to observe last night, I did some thinking about my vertical dimensions. I currently have a 21.5-inch tall pier which at my latitude will put my eyepiece height at 48 inches when pointed 45 degrees above the horizon. My target was 50 inches, so I guess that is close enough. My biggest problem, that was mentioned earlier, is the wall height required, which is 60 inches. I only have 36 inches of wall rings, so I need 24 inches of something under the round wall rings which can also provide an opening for a door, and I need the taller door.

So far, a rock or brick wall was suggested. What I am also considering is, that when they pour my slab, they can create a 24-inch-tall round concrete curb (or wall), but how would a form be made for that? I will ask the concrete guy if that is possible. 

If I have to build something myself, it will be stick built. I can cut out curved sections of half-inch plywood and layer them for base and top plates with 2x3 studs in between. Then use metal sheathing as the exterior wall covering. Well, anyway, I have some time to think about that.

[Victory Pete]

Anything is possible with concrete, even ships.

 

https://www.cloudyni...ild/?p=14027369

 

https://en.wikipedia...i/Concrete_ship

[cavedweller]

Anything is possible with concrete, even ships.

 

https://www.cloudyni...ild/?p=14027369

 

https://en.wikipedia...i/Concrete_ship

 

That thickness is certainly more substantial than I was thinking. I did have the idea that, if I could not find the properly curved blocks or bricks, but then I could mold my own. Make them large, but not too heavy to handle.

 

The second link makes me want to build a concrete ship on my ten acres.

[cavedweller]

I did some on-the-ground work today. I cleared and marked the proposed 12x12 concrete slab area. There are four feet of pavers along the existing concrete, so I moved the dome two more feet away to clear those; I don't want to have to dig them up. I laid out spikes to mark the four corners, the center, and the proposed pier location. I made a sight line towards my estimated north and discovered there is a flat-top boulder about 100-feet away. I placed a small rock on the boulder in the north direction by just sighting along a tape measure. At 100 feet, a one-degree angle sweeps out about 21 inches. I want my pier pointing within that tolerance of north; +/- 0.5 degrees. This equates to only 0.31 inches along the arc 36 inches south of the dome center, so I probably don't need to be so precise (or is it accurate).

As a preliminary test, I setup a tripod and spotting telescope directly over my dome center marker and pointed at a cell tower over four miles away that is exactly east. I rotated 90 degrees back to north and saw my rock within the low-power view. I placed another rock at the center of the view and it was six inches from the first rock. The least accurate of this setup is the azimuth scale on the tripod. One slight nudge, with little to no difference on the tripod scale, resulted in it pointing on the other side past the first rock. Before I call it final, I am going to hope the wind stays away and I can use Polaris after dark. I will need to wait until 3 am for it to be on the meridian.

 

Here is a view from the boulder back to the scope:

 

[Victory Pete]

I used solar noon to get my pier exactly pointing North. I double checked it on 2 consecutive days before I committed to the orientation. I went with a 11.5' x 11.5' concrete pad primarily so I could use 12' 2" x 6"s with only having 2 3" and 2 6" pieces to cutoff. Also, I bought BYO's plans for that size.

Edited by Victory Pete, 02 April 2025 - 07:15 PM.

[cavedweller]

I just finished finding north. I waited for Polaris to be on the meridian at 3:05am local time. I had left the tripod and scope out since earlier and double checked I was still over the dome center marker and tripod bubble level was still in center. I replaced the second rock with a dim red flashlight. It was dead center in view just like I left the rock earlier. I pivoted the scope up to Polaris and it was pointing just a little to the east, so I centered the view on Polaris, and then pivoted the scope back down to my rock formation and the center was perfectly (as close as I could tell) between the first rock and the flashlight. I moved the flashlight to its new position for north and replaced the second rock, as shown in the picture. I pivoted back up to Polaris and it was still centered. I am very confident I now have north marked accurately. I will wait for daylight to check if I need to move my pier marker.

 

[cavedweller]

I am hoping to get an opinion about an idea for a pier foundation. I need the 36-inch offset now, but likely will want a more central location in the dome if I ever change scopes. Instead of a 24-inch round or square, I am thinking 24-inch by 60-inch rectangular block. This would give me from dome center to my max offset in one casting.

 

Would 48 inches deep be deep enough?

[Brian Deis]

I have two wall rings for the PD10 that I was going to put up for sale.  They are in NJ.  Image attached. The door section is not in the image but part of the offer. Let me know if you are interested.

Clear skies,

Brian

Attached Thumbnails

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[Victory Pete]

I am hoping to get an opinion about an idea for a pier foundation. I need the 36-inch offset now, but likely will want a more central location in the dome if I ever change scopes. Instead of a 24-inch round or square, I am thinking 24-inch by 60-inch rectangular block. This would give me from dome center to my max offset in one casting.

 

Would 48 inches deep be deep enough?

My original plan for my observatory was to have an entire 48" thick foundation. Also, I wanted solar panels on the roof. These ideas had been in my mind for 30 years.  There may still be some hope for solar. I think you have a good idea there.

Edited by Victory Pete, 03 April 2025 - 08:24 AM.

[cavedweller]

I have two wall rings for the PD10 that I was going to put up for sale.  They are in NJ.  Image attached. The door section is not in the image but part of the offer. Let me know if you are interested.

Clear skies,

Brian

I will message you shortly. An initial question though; is the door five feet tall?

[Kitfox]

I am hoping to get an opinion about an idea for a pier foundation. I need the 36-inch offset now, but likely will want a more central location in the dome if I ever change scopes. Instead of a 24-inch round or square, I am thinking 24-inch by 60-inch rectangular block. This would give me from dome center to my max offset in one casting.

 

Would 48 inches deep be deep enough?

 

 

I think this is a great idea, thinking ahead.  But the depth is wholly dependent on your soil type and climate, so I can't answer.  In my stable clay and environment, it would be plenty deep.  And you are talking a MASSIVE block, so there is that!