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A housing was needed to protect the telescope from the weather. It had to contain a baseplate to establish the local horizontal surface for mounting the telescope. The roof slope needed to be compensated. Webcams were needed to monitor the internal and the external configurations of the observatory, and the telescope during operation. The internal webcam, directly adjacent to the scope, served primarily as a monitor of the telescope itself. The external webcam primarily monitored the operation of the observatory's lift and rotate operations as the telescope was given access to the sky.
There needed to be lighting so the telescope and observatory could be inspected at night. The housing that contained the telescope needed to be fairly light-tight, so internal lights were also necessary.
The housing would need to open and close, so motors or actuators were needed. Telescope power needed to be remotely controllable. All of this pointed to the need for a relay box that could be remotely controlled via Wi-Fi.
One of my original requirements was that the housing could be closed no matter what the position of the telescope. The idea was that no matter what went wrong with the telescope hardware or software, telescope safety was still obtainable by closing the housing. The first version of the housing was built to meet this requirement. This requirement was eventually dropped because it made the housing so large that it could not be hidden from an observer on the ground in front of the house. In the final design, which featured a much lower housing, it was necessary to stow the telescope in a specific orientation in order for the housing to close. The work-around was that the scope would never be operated if bad weather was approaching and that a ladder would always be available for direct hands-on safety operations.
An additional minor requirement was that the components of the observatory be light enough to hand-carry up a ladder. No penetrations were allowed into the roof surface itself, to maintain integrity for the house below. The final configuration also had to be heavy enough that high winds would not move it, but not so heavy to load the roof excessively. The only wiring necessary was to be AC power. No lightning protection was added. The housing had to survive heavy rain and snow, yet be lightweight. All parts had to be stable, RF transparent, and no wood permitted unless pressure-treated.
I looked at all the standard observatory designs: roll-off roof, dome, clamshell, etc., but none had a profile low enough to meet the visibility requirement from the front of the house. All of these requirements led to a design where the housing would be a box divided into a non-moving lower half and a lid that, once lifted, could be swung out of the way. For box lightness, I chose 1" thick closed-cell foam sheets. For lifting the lid I chose a linear actuator that I had as a spare to my larger scope, and rotation of the lid was through a small table sitting on a large circular bearing, driven by a reversible motor driving a belt.
A small box of electronic parts, some under-the-cabinet LED lighting strips, and a Wi-Fi relay box completed the main elements. Pivoting parts were to be made of PVC pipe and threaded rods. Of course, the observatory design had to be worked in parallel with the development of the telescope. Here are some of the construction photos:
The original box housing and the observatory floor with internal aluminum plate for telescope mounting. The foam pieces were screwed together with 3" drywall screws after the sheet edges were glued. The aluminum baseplate did not touch the white azek floor.
On the left below are shown the circular bearing, its mounting plate, and the lower box section with the cutout for the aluminum telescope plate. On the right is the first cut at the lid-lifter with linear actuator (12" throw). The actuator and its hinges, were on an azek square that rode on the circular bearing. The idea was for the lid to lift, then the table to rotate 180 degrees.
Below: The electrical box for observatory control. It contained the power bricks for the webcams and the relay box, the relay box itself, and the scope. A webcam protruded above the surface of the electrical box. The assembled of the observatory was tested on my roof slope simulator. Note that the box lid was much shorter now and that the mechanics of the lid lifter had been rearranged. Note the aluminum tape applied to the lower box mating edge. This protected the foam and provided a good sliding surface. The lower inner edge of the lid was similarly protected.
Here's the modified ladder, below, that I used for roof access. Left image is the ladder wheeled into place (every ladder needs wheels, right?), right image shows the 'walk-through' modification I made to avoid having to swing my legs across the ladder when getting down.
Installation!
The pieces were hand-carried up onto the roof. The eight concrete pavers are weights to stabilize the observatory in high winds. The bucket and drill were to hold and to mix yet another epoxy batch. An aluminum sheet with bolt tie-points was epoxied directly to the roof shingles to provide as rigid a connection as possible to the building. My brother Joe helped with the roof connection, and aided me on the lifting/lowering of the scope (40 lbs) from lab to roof. The scope went back down to the lab at least a half dozen times for repairs over the course of the project.
The cutout in the azek floor allowed access to the shingle-epoxied aluminum sheet that would support the scope. The cutout provided isolation between the scope and the observatory structure. The pavers were loaded onto shelves below the floor as ballast. The entire observatory was held in place by gravity and friction only.
Two images below, the observatory opened, and partially closed. Video of the open/close operation is here.
The observatory installed, October 2019.
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