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Build Log: Dome Annex to Existing ROR

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#1 MJB87

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Posted 26 March 2021 - 08:29 AM

This is a build log for a dome “annex” to an existing ROR. It is offered here to help others who may want to embark on a similar journey. It will be posted in two parts. This is part 1.

 
Rationale

 
First, why do this? My setup was a side-by-side installation of an AP 130mm Starfire GTX used for DSO imaging and a CFF 300mm classic Cassegrain used for visual, EAA, and planetary imaging.

 
Adding a dome to my existing ROR addresses allows me to split up this setup and solves several issues. First, the side-by-side arrangement makes it more complicated to view over the sides of the ROR for the telescope on the “down” side. Second, there are times I want to have the GTX off imaging and I want to look at different stuff with the CFF. Finally, putting the imaging setup in a remotely controlled and automated dome allows for the possibility of longer imaging sessions while I sleep.

 
Design Concept

 
Linking my dome with the existing ROR allowed me to share power and data already linked to the ROR. I can also have a common work and storage area (in the ROR) to run both observatories. It also avoided the need for a new building permit. While the buildings are linked, they are also structurally independent: they share no load-bearing walls.

 
It made sense to place the annex on the east of the existing ROR. The roof of the ROR will block the view to the west from the dome (though I can move it if needed), and the dome will block the view of the ROR to the east. However, those views are already compromised by trees. I can place the dome close to the ROR because I do not plan to open the lower shutter due to light pollution, poor seeing at low altitudes and trees blocking the western horizon. However, if I need to, I can always open the ROR to allow for unrestricted opening and rotation.

 

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Height management became the vital issue in the design of the dome observatory. I wanted to have six feet of clearance for walking in the annex, but I wanted to minimize overall height of the dome. My architect/builder designed a post-and-beam system using pressure-treated 4x6 timbers that minimizes the height of the roof structure. The height necessitated a high concrete pier 26” above the rough floor (and five feet below it). We decided to do the concrete pour in two phases to allow for precise height measurement once the dome was installed.

 

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On top of the concrete pier I installed a 54” high 10” diameter ATS steel pier. In total, the base of the telescope in the park-4 position is 93” above the rough floor. This gives me access to all altitudes above 24° to 27° across about 90% of the horizon and from 27° to 33° around the rest.

 
I considered several dome options but ultimately chose an ExploraDome with the full MaxDome II automation setup.

 

Basic Structure

 
The dome annex is a 10’x10’ building supported by eight 4x6” pressure-treated posts on concrete footers with a concrete pier base that extends three feet below ground and about a foot above it, with rebar extending several feet further up to allow us to tie in the second concrete pour for the base.

 

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Exterior walls are Hardie planks that match the current ROR. All of the trim is Azek – no wood is exposed to the element except the pressure-treated timbers.

 

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A circular platform supports the base ring for the ExploraDome.

 

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The roof is white TPO. It was important to have good flashing into the existing ROR structure. The only potential issue will be snow, which is relatively rare in this area. I might have to brush off the snow in the section between the buildings.

 

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We cut a passageway between the new annex and the existing ROR. We also removed a small air conditioner from the ROR and installed a slightly larger unit in the annex, opposite the passageway. There is a window above my desk in the ROR that allows me to see the dome telescope. This setup allows cool air to circulate between the structures in the hot summertime. I can also control the new air conditioner via my iPhone.

 
Dome Installation -- Structure

 
The aluminum base ring and the ring on top that supports the dome were straightforward to install. A fair amount of time was spend using a laser level to insure it was all level.

 

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We installed the dome itself using only three people (but it would have been easier with 4). The next step was to install the hold-down rings on the inside of the dome skirt. There were small gaps between the underlying wooden ring and the dome ring – these were filled with expanding foam. Overall, dome installation was not that difficult and took three people about two hours.

 

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Dome Electrical / Mechanical Systems

 
Some challenges emerged around the dome’s electrical and mechanical systems. Most fundamental is a complete lack of any documentation on how to install the various motors, brackets, battery housing, pre-assembled controller units, electrical connectors, etc. that come with the ExploraDome and full automation kit. This is because ExploraDome just switched from the Foster System to the MaxDome II system. I needed to sit back and work from first principles – look at each piece and figure what it must be for and what it must connect to. I also got excellent advice from fellow CN’ers who have been through this. Here are some of the specific challenges that emerged.

 
First, if you get the dome pre-assembled with shutter opening systems installed, you need to be able to close the shutter (the dome is shipped with the shutter open) and you can only do that using the motor.  The wiring connections used by ExploraDome are Molex connectors with 14-20 AWG .093" pins. It is helpful to prepare a cable in advance that you can use to connect the shutter motor to a battery to open and (by reversing polarity) close it.

 
Second the bracket for holding the rotation motor shipped with the automation kit was in my case improperly specified – the mounting holes misplaced by 1 ½”. It was also improperly assembled when shipped. There was no way to mount the motor in that configuration.

 

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The gap meant the rotating gear teeth would not contact the mount rotation ring.

 

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ExploraDome immediately shipped a modified bracket of an earlier design that worked fine.

 

Data and Power

 
Power and data cables are routed been under the floor of the observatory and up into the concrete pier.

 
There are four 20A circuits serving the existing ROR. Two of these are extended into the annex, one to power the mount, cameras, and other devices on the pier and the other for lights (one red and one white) and receptacles. I checked all of the loads and it will work fine. All receptacles and light fixtures are rated for wet conditions – just in case.

 
A managed POE switch in the new annex connects via fiber to the existing switch in the ROR, itself feeding back into main switch 800 feet away via fiber. The switch will connect to the mount’s CP5, the rain/cloud sensor, a weather station, and some other devices. Powered USB hubs will connect cameras and other devices on the pier to the computer workstation in the ROR. I also took this opportunity to (finally) upgrade my GTOCP3 controller on the existing 1100 mount to the GTOCP4 controller that has been sitting in a box for over a year.

 
All of the electrical AND data connections have inline surge protectors, primarily to protect against nearby lightning ground strikes.

 
Ancillary Systems

 
A SkyAlert-E is installed for weather detection and automation shutter closure should circumstances warrant. An air conditioner is installed – it gets hot here in the summer – for those cloudy days when daytime work inside the observatory is required. Four surveillance cameras monitor the inside and outside of the observatory, complementing the other three already installed in the existing structure. The observatory has its own weather station.

 
It was now time to install the mount and telescope (part 2 in the next post)...


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#2 MJB87

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Posted 26 March 2021 - 08:44 AM

This is part 2 of the build log...

 

Once the structure was mostly complete we poured the concrete for the upper part of the concrete pier and installed the j-bolts for the steel pier.

 

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My builder knew his stuff – we ended up with only about a gallon of extra concrete.

 

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Interior Finishings

 
Interior finishing and electrical installation followed. We chose pre-primed pine lap boards for the walls and painted them a dark blue.

 

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The doorway between old and new rooms was cut in and framed out as was a window that allows me to see the scope from the primary workstation in the old observatory.

 

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Final Configuration

 
A big moment came once the concrete had cured and we were able to install the steel ATS pier. It was at this point I was able to check final heights and found I was within ½” of initial plans.

 

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It was also possible to start wiring up the data and network cables and start systems tests. (I’d “pretty it up” later.)

 

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One of the challenges was in connecting the dome shutter controller unit to the master controller unit that controlled rotation. The connection method is via signals sent over two magnetic induction loops, one on the fixed base of the dome and the other on the flange connected to the rotating part of the dome. It took a while to get it all sorted out but it works. (Ignore in the photo the second wire on the bottom – that was an earlier approach later discarded.)

 

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Slight panic ensued when the SkyAlert connection failed. A test of the Ethernet cable, supplied with the SkyAlert and unique to that system, indicated that not all of the wires in the cable were operating.  An exchange of emails with the folks at SkyAlert confirmed that not all of the wires were used and it turned out to be a slipping RJ45 terminal in the actual SkyAlert unit, since corrected.  I can also confirm, with embarrassment, that plugging the SkyAlert cable directly into a POE+ (44v-57v) switch, rather than using the dedicated POE injector at much lower voltage (9v), does not “fry” the SkyAlert electronics.

 

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Installing Mount and Telescope

Initial testing of the dome rotation and shutter, once the bugs in the magnetic induction loop antenna were fixed, went smoothly. It was time to install the mount and telescope. (I left the final cable management to a later time once the configuration was stable.)

 

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Installation of the CP5 control unit was complicated by the large diameter of the pier, larger than the standard piers A-P usually delivers. I used 3” long 1/4-20 hex-head bolts and spacers to allow me to clear the pier diameter.

 

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Mount testing began. It was at this point a problem emerged. In certain locations, the mount would move smoothy and them emit a horrible noise I can only chracterize as a “raspberry” type sound.  I immediately posted a note on the AP GTO forum and Roland himself responded within a few hours. I send him a video clip illustrating the sound. Roland advised me to visually inspect the worm gear, informing me that what I was hearing was a stepper-motor stall. In doing the examination I found a washer on the surface of the worm gear.

 

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Roland explained that the washer was causing the stepper motor to stall as soon as it made contact. I did a full visual examination of the worm gear and found no issues or apparent damage.

 

Roland then asked me to check the four screws that hold down the RA axis motor. Sure enough, two of them were missing and another washer was found in the motor housing. The screws were never found. Replacements arrived overnight the next day and were installed. Roland informed the AP GTO forum that he took personal responsibility as it is he who does the final motor mount adjustments. He must have failed to install two of the screws after making those adjustments. He is changing the process to make sure a similar problem does not emerge again.

 

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Setting Up Dome / Mount Geometry

 
It was time to set up the configuration of the dome/mount geometry. Horizontal and vertical dimensions were made using a laser measuring device. We estimated the center of the dome rotation, attached a plumb bob to a string at that point, and rotated the dome, observing how the plumb bob rotated around a 2” circle. The middle of that circle established the center of dome rotation.

 
The new Ascom Device Hub utility made setting up the dome and mount relatively simple. Once the measurements were entered the dome and mount moved together. A times the control of the dome and mount in operation will be via TSX which, unfortunately, used a different terminology for E/W and N/S offsets. The TSX manual is quite vague on this. It took a few minutes to sort that out.

 
Final Steps

 
The telescope and mount are installed and checked out. The new ASI2600MC-Pro has been installed and checked out. Polemaster was used for polar alignment. Horizon limits have been set and and an initial APPM model has been created.

 

The mount points and tracks very well. I am getting good 5-minuted unguided images. The basic system is operational and now I'm working on the details of automation. SG Pro will allow me to automate all of the steps except turning off power to mount and camera. That is the next step.

 

Some Final Observations...

 

The whole project took about 8 months from concept to completion. There were the usual challenges along the way. In the end, however, I got outstanding support from the equipment suppliers.  Dustin at ExploraDome was always ready to provide advice and offered to walk me through systems installation on the phone, though in the the end that wasn't needed. Roland Christen at Astro-Physics and Ray Gralak at Sirius Imaging have been readily accessible and have helped sort out minor issues.  Wes at Interactive Astronomy (SkyAlert) has provided excellent support.  I am reminded how fortunate we are in this hobby to have such excellent suppliers.

 

Marty


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#3 descott12

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Posted 26 March 2021 - 09:17 AM

Looks great. I envision something very similar in the not-to-distant future.
Question: how did you seal the dome ring to the new roof? I think that would be you biggest risk or leaks.



#4 MHamburg

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Posted 26 March 2021 - 10:01 AM

That is a very professional-looking construction. You mentioned that you get little or no snow, but just in the rare case that you get any ice accumulation, it might help if you install a heating cable in the area between the dome and the adjacent building. Where I am in the Berkshires, snow and ice are the rule .

Michael

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#5 MJB87

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Posted 26 March 2021 - 10:21 AM

Thanks for the feedback.

 

In terms of ice, we get about 1-2" of snow about once every other year. That's it. It rarely lasts more than a day or two.

 

Yes, the people who built the dome also built my new home a few years ago. The home is extremely well built and won several major architectural and building awards. The builder knows what he is doing. Their crew put on the new annex on weekends in-between their other projects.  I helped the carpenter quite a bit and while I've always been proud of my skills, this pro made me look like a real amateur.  BTW, if anyone in the Delmarva area is thinking of building a dome, I now have a well-trained and experienced builder to recommend.

 

In terms of dome flashing... The dome base ring comes with a 4" or 6" aluminum skirt (I forget which) that fits over the structural ring built into the roof. We sealed it with marine sealant when we lowered it into place. The TPO material comes up and over the structural ring forming flashing. I "splurged" on some real roofers to do this right. So far it has been very tight. I'm fortunate in that I live in a boating area and there are lots of good marine products available nearby. For example, I used one of these to run the SkyAlert RJ45 connector/cable through my exterior wall. Very tight.



#6 Genoafire

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Posted 09 May 2021 - 04:12 PM

Thanks for sharing Marty.

I just ordered the 8 foot Explora-Dome myself with the full automation kit. When I spoke to Dustin he indicated that the dome is going to arrive with everything installed all the motors etc. and they pre-test everything before leaving the “factory”. So I was a little surprised in your post about the bracket not fitting properly. If they do truly install everything before shipping maybe this is a recent change as a result of your problem? I must agree that Dustin is very helpful and spent a lot of time on the phone with me. I am very interested in your double build, so to speak ,as I will be using it for something similar. I have a Takahashi TOA 130 on a 10Micron mount for Astrophotography and I also have a 24 inch StarMaster Dobsonian for visual. The Starmaster has wheelbarrow handles to move it around. So my plan is 100 ft.² for the dome and 100 Square feet for an adjacent room to house the Starmaster.  Our county building codes limit the size of a non-permitted building to 200 ft.². I will have a concrete ramp and walkway on the starmaster side leading to a 3’x3’ concrete observing area in the grass nearby, so no roll off roof. The access to the dome will be a full-size man door.  So my building will be quite tall to accommodate my height, like yours. The Starmaster side will have a rollup garage door sized to fit. How is your ExploraDome working so far with the MaxDome II software?  
thanks so much,

Bob



#7 MJB87

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Posted 10 May 2021 - 06:37 AM

The dome itself arrives with the actuators, limit switches, etc all installed.  However, the dome and the supporting rings are packaged separately and the dome rotation motor, bracket, etc. are not pre-installed. Nor are the electrical and data connections between rotating dome and fixed dome base. (They couldn't be given how it is shipped.)

 

When it comes time to assemble the systems the local installer must

- Make the electrical / data connections for the shutter system to home position charger and controller box #1

- Install the rotation motor, bracket, etc.

- Install the charging pad and proximity sensor to establish dome home and recharging position

- Make the electrical / data connections for the rotation motor to battery and controller box #2

- Install the magnetic influence system to link rotation controller (#2) with shutter controller (#1)

 

There were zero instructions provided with the kit for these five items.  I was able to figure it out (relatively easily) with the help of CN members with ExploraDomes, especially KathyAstro and some folks on the MaxDome user forum. Dustin offered to walk me through it on the phone if needed but in the end it wasn't needed.

 

One thing to note: the shutter is shipped open. You can't manually close it -- it has to be done with the motor. Prepare a charged battery in advance, ideally with a Molex connector, so you can connect the shutter motor up to power and use that to close the shutter once the dome is up on the observatory.  (This would be handy, for example, if you are expecting rain before you can set everything up.) I'm happy to send the specs for this Molex connector once I get back home. (I'm on the road.)

 

Finally, by all means reach out for help.  I'd be happy to take you on a Facetime/Zoom tour of my installation and other wise help you through the process. A video can be worth 10,000 words. Send me a PM if/when you'd like to do that.

 

Marty


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#8 Genoafire

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Posted 10 May 2021 - 09:54 AM

Thanks so much for the fast and detailed reply Marty. I will contact you as suggested once I receive the dome.

All the best,

Bob



#9 MJB87

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Posted 11 May 2021 - 08:27 AM

No worries, Bob. Just send me a PM when you are ready.

 

Marty


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