Meadowgold Mobile Observatory
For quite some time I have wanted to build a mobile observatory. The night sky at my home is OK for observing, but not great – rated a Bortle 5. So a goal was to have something that can be set up and ready to use at home, but portable enough to take to a dark site and enjoy observing there.
Enter the Toy Hauler
I was looking into toy hauler campers, which are, as the title suggests, RV trailers meant to haul ATVs, etc while also having a living space. I ran into the front deck toy hauler design and knew immediately this was the best shot at making the mobile observatory.
I found a really clean used Forest River front deck toy hauler that some nice folks in Michigan had for sale, and purchased it in Fall 2019.
Choosing the Dome
The deck on the toy hauler was 8ft square, so there were several domes available that would fit on that size deck. I chose to go with NexDome, mainly on a cost/features comparison. It had everything I needed.
I’ll have a separate writeup on my thoughts on NexDome, what I like, what I don’t, and some changes I have made to my dome.
Placed the order and had lots of time while waiting to work out the next challenge – mounting the pier…
Mounting the Pier
Since starting this project, I had continuously been pondering how best to stabilize a pier in this kind of system. I knew it had to be isolated from the trailer and very solid.
I arrived at a 3 legged tripod for a triangle base that the standard NexDome pier would bolt onto. This was the simplest to fabricate. The legs would be square 5000lb capacity trailer jacks with a hand crank. Getting the size just right was important, to have the legs miss the floor supports of the trailer deck, which were 16″ on center.
I had this fabricated by the great folks down at Wolfe Metal Fabrication in New Kensington and it turned out great. I planned 3/4″ steel, but they had some 1″ instead, so I figured why not? The heavier the better!
Borrowed a magnetic drill press from my brother, and drilled all the holes. Broke one of his bits — sorry.
Assembling the Dome
Making it Roadworthy
It goes without saying that the NexDome was not intended to travel down the highway on a trailer, at highway speeds with wind and the elements. The dome itself rides on rollers and only its weight holds it onto the walls. Some steps had to be taken to make this rig roadworthy so it could withstand traveling.
First, additional bracing was added from the walls to the floor. This bracing is removable if I want more room inside after traveling.
Also this image shows the ABS plastic sheets that close up the holes in the floor and slide nicely as the trailer moves separate from the mount.
While in transit, the pier is strapped down with cargo straps to the floor of the dome to prevent it from moving. The scope and counterweights are removed in travel, but the telescope mount itself can remain on the pier.
A full custom tarp was built to cover the entire dome and serve to both protect the dome as well as help hold it down onto the trailer.
The Warm Room
My goal is to be able to run the entire trailer using battery power if no electricity is available.
First, this requires that all equipment can run from 12 volt DC. I found Spectre brand monitors that run on 12V, and my laptop can run from 12V. Of course all the scope equipment and mount can run 12V. The trailer is already suited to run lights, water pump, refrigerator, and furnace from 12V and propane.
I found a toolbox that mounts on the trailer A frame tongue and holds 5 deep cycle batteries, giving me a total of 450 amp-hours of power. This should be enough to run several evenings.
In the warm room, I run (2) 30-amp circuits to a control box at the desk. There, I have a control box to select (6) different 10-amp circuits for the various components. Voltmeters and ammeters allow me to keep an eye on the current draw, to watch for problems like a motor hanging up.
Both AC and DC power is monitored by power meters. The AC side is useful for monitoring how much AC power is being used when plugged in at a star party. The DC side has a Coulomb counter to measure the amount of energy used and the amount of energy remaining in the battery bank.
The Pi controls everything in the observatory. Inside the warm room, I connect the KStars application to the Pi4 server.
The Raspberry Pi is a Pi4 in a Vilros case with a fan. I have included a real time clock module, which was a little challenging to fit in the case. Bending the pins over allowed it all to fit.
Keeping Tabs on Things
It is surprising how unnerving it is to command a telescope mount to slew and not be there to watch it, to make sure everything is going OK. What if a cable gets caught, or the coordinates are wrong? It is nice that I have a power control box next to me in the warm room, but without eyes on the scope, it isn’t much help.
So, that was addressed with … more cameras.
These little cameras are inexpensive and easily mountable: ELP Sony IMX322 USB camera with 170deg lens
Mounted two of them in the dome. One to view the interior of the dome, and another on the scope to see where it was pointing. This helps ensure that the dome is rotated to the right place for the scope to see out the shutter opening.
For these cameras, I added .. yet another Raspberry Pi. This one runs MotionEyeOS, an open source security system software. So in a browser window, I can keep tabs on everything in the dome:
Preparing the MMO for a dark site involved adding blackout blinds, and shielded red lights to illuminate the steps at night.
There are features of the NexDome that need to be improved. The shutter needs to work more smoothly, and the dome slaving to align the shutter opening with the telescope is not as accurate as it should be.