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Xodus Observatory at the Old Nashville Zoo Build Log

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#1 Omeganon

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Posted 26 July 2021 - 11:04 AM

Hi all! As it seems to be tradition, I'm going to post updates of my observatory build for all to see. Hopefully the learnings from it will go both ways.

 

I live on a heavily wooded 5 acres of land, most of which has slopes > 20 degrees so I don't really have any options on my own land. I do, however, live right next to 119 acres of land that used to be the Old Nashville Zoo. I have permission from the owners to build my observatory in the field that used to house the giraffes and elephants --

 

Giraffe and Elephant field

 

Tennessee Game Farm
 
In the aerial picture, the elephant barn still exists in the top left, while just the concrete pad for the giraffe barn pictured above remains in the top right.

 

I have purchased a Nexdome, extra bay, permanent pier, shutter kit, and the dome rotation kit. I made that purchase in January and they arrived just over a week ago.

 

Nexdome arrives

 

For my basic layout, I'm going to be doing a 12' x 16' concrete pad, with an isolated pier offset to the west side, leaving room for chairs and the occasional use of my Z12 dobsonian for visual on the east side of the pad. I'll be using a 2' diameter drain pipe that I had on hand as the form for isolated pier foundation. This view faces due south (and southwest for the second picture).

 

Basic layout
 
Concrete for the pier base

 

This past weekend, we dug trenches for the outline of the pad and laid conduit from the pier base to the south side and eventually it'll extend power to my home. We're also planning for optional solar charging if we decide against running permanent power to the house. We also added a couple of inches of gravel as a start of a base for the pad itself.

 

Outline and conduit trenches dug
 
Pier base form graveled in
 
A layer of gravel for the pad
 
For the pier base itself, we built a simple rebar frame. As my frost line is only about 3" where I live, I didn't have to dig too deep of a hole for the base; going about 12" beneath the current ground line. The pad is expected to be 5-6" thick.
 
Rebar in place
 
For isolation, I lined the inside of the form with 1/2" gym floor mat before adding the concrete.
 
Vibration dampening courtesy of ‘gym floor’ mats from Amazon

 

I also prepped the template of my pier bolt pattern with 10" anchor bolts.

 

Nexdome permanent pier template
 
Nexdome permanent pier template

 

We added the concrete and set the template into the base.

 

Mixing the concrete on a hot hot day
 
Anchor bolts set
 
And because I seem to have a Plasti-Dip fetish (is there a 12 Step out there?), I coated the outside of the form to darken it and just generally make it look better while I'm waiting for the concrete to cure.
 
Waiting for the concrete to cure. Plasti-dip the outside of the pier base.

 

 
No exact ETA for the concrete for the pad, but I expect to have that formed and pored in the next couple of weeks. In the interim, I'll be installing the permanent pier as my next milestone.

Edited by Omeganon, 26 July 2021 - 11:48 AM.

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#2 Omeganon

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Posted 26 July 2021 - 11:39 AM

Just did a test fit of the pier to make sure I did the bolt pattern right. Slips right on...

 

Pier test fit

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#3 eastwd

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Posted 03 August 2021 - 09:25 PM

Great start! Thanks for sharing this, and please keep the posts coming.

#4 Omeganon

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Posted 04 August 2021 - 02:24 PM

Got the pad poured yesterday --

 

IMG 0613
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Arial time-lapse -- https://youtu.be/NxqOM5RXZb4


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#5 Omeganon

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Posted 05 August 2021 - 11:20 PM

Pier and mount set up. I used a bit of Sea Deck under the pier for aesthetics only. 
 

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#6 Omeganon

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Posted 09 August 2021 - 12:06 PM

Had a good weekend of progress on building the actual dome.

 

Dome bays -

 

IMG 0649
IMG 0650

 

Dome walls -

 

IMG 0654

 

Dome partially constructed -

 

IMG 0656
 
And placed -
 
IMG 0662
 
Anchoring the walls - 
 
IMG 0669
 
End of weekend - 
 
IMG 0665
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Time-lapse of the build here - https://youtu.be/nJXE5RvC1BA
 
The hardest part is absolutely the dome itself. It can be a challenge to line up the holes needed for the screws where 3 pieces join. The new rail system is also a pain in the butt to install right. I've made 3 attempts at getting it right, taking it apart each time, and the shutters still don't slide smoothly. Major pain point is that the rails are designed for a 'perfect' dome curve and are rigid, while the dome itself is only semi-rigid and can have variability in all directions (height, diameter, spread). Getting the dome to conform to that ideal curve is challenging. I need to take it apart at least one more time. Having the extra variability of the in/out adjustment of the wheels themselves is a mixed blessing. The T-slot bolts are also meh to get lined up where they need to be without sliding to the bottom of the rail. Definitely a 2 person job.
 
There's also an undocumented front and back to the dome itself that only becomes obvious when you have it all together and get the the last page of documentation of where to put the shutter stop block. I'm not going to take it _fully_ apart to redo that and will just come up with a different solution to the problem.
 
finally, there seems to have been different bit sizes used on holes that are supposed to line up. I needed to drill a few of them larger to accommodate the provided bolts for those, mostly affecting the top left hand side of each panel when viewed from outside.

 


Edited by Omeganon, 09 August 2021 - 12:06 PM.

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#7 Omeganon

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Posted 26 August 2021 - 01:58 PM

It's been a while since I've posted more information on the build -- Weather wasn't cooperating and I had a delay waiting for some replacement parts (more below).

 

After I got the rails and shutters on, and back on the dome, I found that the shutters kept jamming on the new tracks. They'd either get wedged on top of the rails, or even behind them. They'd get locked up and took a lot of effort to free them up again.

 

IMG 0723
IMG 0725
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I reached out to Babak and they sent me new rails the next day... They took about a week to make it to me through customs. In the meantime, I saw that the stopping block they sent for the back shutter was going to be too far back and not allow the front shutter to completely close as others have seen. I modified it by using an L-bracket as a stop at the right location.

 

IMG 0729
IMG 0731
 
I also worked on the exercise mat flooring inside the dome.
 
IMG 0735
 
Finally, the new rails arrived and I was surprised to discover that it is yet another new design. Instead of 2/3 + 1/3 aluminum rails, they're 2 50/50 HTPE rails with a different profile.
 
IMG 0743
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IMG 0745
 
They're muuuuuuuch easier to install than the aluminum rails. No more t-bolts and only 2 bolts per track segment. None of the existing holes in the dome lined up so I had to drill new holes, but that's no big deal. Once installed and back on the dome, the tracks slid very nicely.
 
IMG 0749
IMG 0754

 

011DCDE1 8B94 41C9 A298 E5C2E6457E31

 


Edited by Omeganon, 26 August 2021 - 02:01 PM.

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#8 Omeganon

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Posted 01 September 2021 - 11:34 AM

Once I had the shutter rail system working well, I looked at attaching an RG-11 rain sensor to force a closure of the shutter if it rained. More context around that at https://www.cloudyni...ver-controller/, but that ended up working well. I did a bit of crafting and made a ethernet-based connect/disconnect so I can move things around without needing to actually re-wire either end. You can also see the TP-Link EAP225-outdoor wireless antenna that I'm using to extend a wireless network across the entire field.
 
IMG 0783
IMG 0784
IMG 0791

 

Next up, replacing the rubber straps that were sent that secure the dome to the walls in the event of high winds. One of them had already torn with just a little bit of tension while attaching it so I wasn't impressed. Crafted these using paracord and quick connect clips.

 

IMG 0806
IMG 0807
 
Command and control system for when I need to do work in the observatory.
 
IMG 0775
 

Security is important since there's a lot of high-value equipment in the observatory. It is in a very out of the way place and it can't be found unless you know it's there, but covering my bases, I have a Nest Protect installed for fire detection + fire extinguisher, 2 internal cameras (Wyze pan/tilt and a Nest Cam), and 1 external camera.

 

IMG 0803
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For power, I have a 400 amp/hr 4-battery, Xantrex PowerHub 1800 Solar Generator. Solar isn't attached yet but will be 2x 140 watt panels. You can see the battery bank in a bay in a picture further down below.
 
IMG 5413

 

And we're largely caught up. Current state and my first-light image of IC 1396, the Elephant's Trunk Nebula.

 

IMG 0778
IMG 0808
LBN 451 Elephants Trunk Nebula
 
A short video of the Observatory in operation at https://youtu.be/WrddLJCCGS8

 


Edited by Omeganon, 01 September 2021 - 11:54 AM.

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#9 Omeganon

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Posted 24 September 2021 - 12:00 PM

Some updates since my last post --

 

Got frustrated enough with the shutter charging system to implement a new way of doing it (as seen on Facebook). So far so good. --

 

Charger Change
Charger Change

 

To help further waterproof the door, I crafted an awning for it out of HDPE and car door seal from Amazon [1] --

awning
awning
awning
 
Also beefed up the observatory security a bit --
 
Security
 
In the works -
 - I'll be using flex brush weather seal [2] to provide a more weather/bug resistant barrier around the perimeter of the dome/wall interface, as well as the back of the shutter. I'm printing some clips for those right now and will hopefully be able to work on that this weekend.
 
 

Edited by Omeganon, 24 September 2021 - 12:01 PM.

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#10 Omeganon

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Posted 26 September 2021 - 05:38 PM

Super happy how my brush skirt project worked out. Designed and printed the clips needed to hold it in place. Preliminary tests all look good. Dome rotates without issue in both directions (as expected).

 

Published on Thingiverse if anyone else wants to give it a try - https://www.thingive...m/thing:4975452

 

It uses ~25' of the 2" brush door seal from https://www.northsho...l-b07-flex.html

 

IMG 0918
 
IMG 0919
 
IMG 0920

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#11 jfgout

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Posted 27 September 2021 - 08:48 PM

Very nice looking observatory!


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