Observatory

Been on a hiatus for a while now, but meanwhile I have been scheming to construct an observatory. The detached room we have in the backyard provided for a very good skyline and height to build this. After researching on the web, I pretty much narrowed down my decision to something like this (or this). After talking to Richard Shell from STI, and looking around for the right shed, I finally decided on an Arrow Newport Shed from HomeDepot which was on sale for 230$. Richard suggested that instead of the 2x4 and 1x4 rails, he is now using garage door rails and it works much better. But this would add some more engineering to the project and so I decided to do this with 1x4s and 2x4s with castors.

We were getting a new roof constructed on the detached roof and my roofer was kind enough to listen to what I needed and built me a counter leveled platform for my shed. He also installed braces for the 4x4 columns. The platform were built with these dimensions (this is from the shed manual):


The platform and brace for the columns eventually ended up looking like this:
Platform from the front
Platform from the back
4x4 column brace

The platform is counter leveled to correct for the slope in the roof and make it flat. And the braces are leveled as well. The height difference between the two braces (because of the slope in the roof) was corrected for by using different length 4x4 columns. Anyways before we get ahead of ourselves, I had to buy all the lumber. braces, castors etc. for the roof frame, the rails and the columns. I drew up this design before acquiring the lumber:

This changed a bit as I started building, but the roof frame was pretty much spot on. As you can see from the above, the roof frame and the part of the rails on which the castors ride are made of 2x4 bars. The side stops on the 2x4 rail is made of 1x4 bars and the rail support in the back is made of 4x4 columns (attached to the 4x4 brace in the bottom)

Basically, when constructing the shed off of the instruction manual, you just skip the parts where the roof is affixed to the walls through the wall channels. Instead the roof is constructed in completion and attached to the 2x4 frame using wood screws. The rest of the building (base frame, walls, wall support channels, doors etc.) are again constructed according to the manual. One the walls are all standing up, you build the rails on top of it and then place the roof on top of the rails. The rails were originally going to be build with a complete four sided frame with the two side portions running further back so the roof can roll off to the back. But then I realized that I did not need all four sides. In fact I only needed the two sides on which the castors would roll. So eventually I just ended up doing this. Also the length I used finally for the rail 2x4s was 139 inches as opposed to what I had in the diagram to begin with. On either side of these 2x4 rail supports (which are laid flat on the roof, screwed with wood screws through the side wall channels and supported and screwed into the 4x4 columns in the back), I used 1x4 bars to provide for wheel stops, so that the roof does not slip off the 2x4 rail by moving sideways. This creates a depressed channel in each rail in which the castors ride. Blocks of wood are also screwed in these channels on either end so the roof can only move so far in either direction
The rail design using the 2x4 for castor support and the 1x4 for wheel stop on the sides forms this depression in which the castors ride
Here are the end stops which make sure the roof does not travel more than it should. 4 such blocks on the 2 rails make sure that the roof only goes so far in either direction
Castors sitting inside the rails
The 2x4 castor supported is screwed on to the wall channels from underneath using wood screws

I then built a pulley system using nylon ropes and metal rope eyes so I could pull the roof on and off from below without having to climb up on the roof. Basically it uses two pieces of rope on either side so that there is no rope in the center obstructing the view and uses metal eyes and rope knots to acheive the right forces to move the roof in either direction. Each side is composed of 3 eyes. One of the roof frame (eye 2) in the front and two on the rail system one in the front (eye 3) and one in the back (eye 1). The rope passes through the eye 1, enters eye 2 where it's knotted and then passes through eye 3 and then back out through eye 1. These four ropes then pass through two additional eyes on a beam fastened between the 4x4 columns and reach the ground in the back where they can be reached and pulled on. When the top ropes from the two sides are pulled, because of the knot on eye 2, the roof starts rolling off. when the bottom ropes on the two sides are pulled, eye 3 directs the force forward because of the knot in eye 2 and hence the roof starts rolling forward. It is important to note that when the roof has completely rolled on eye 2 should be a little behind eye 3. The forces act in such a way that when rolling the roof on, the forces on eye 2 act horizontal only as long as it is behind eye 3. Once it gets on top of eye 2, the force becomes vertical and the roof won't move anymore. Some pictures might help:
A full view of the ropes inside the building. This is the right side looking from the front of the building
Eye 2 and eye 3 setup when the roof is completely rolled on. Notice the knot on eye 2. This is what lets the forces direct the roof on and off
Eye 1. This eye is used to just direct the ropes out of the building while staying on the edges
These eyes in the back take all four ends of the ropes and direct it down from where they can be acted upon. You notice that ropes from one side of the building go through one eye. The two eyes here are centered so that there are no lateral forces when yanking on the ropes. The length of the two pieces of rope from either side (top part or bottom part) are tied together so they form two coherent pieces, one which moves the roof off and one which moves it on
A view from the back of how the ropes travel behind the building
Another view
A view from down below where the ropes will be used to roll the roof on and off

And here's with the roof off and on:



When the roof is off there is a pretty good, clear view of the sky, and the telescope should be able to slew to it's limits through the zenith. The view to the back is not much limited either (the horizon is above the level to which the rolled off roof obstructs the view and the roof itself is not very tall, even with the castors and the frame. Atmost 6~8 inches)


Another idea I had (what with 100 degree days in NorCal these days) is to have some forced ventilation in this observatory. I found these solar powered vent fans which were a great fit. I installed two of these in the center roof panels after cutting the right holes. Caulked it afterwards to be water tight. They work great!
The solar panels can be seen on the outside
view from the inside

A full view of the observatory:



And a video of it in action ;)


Also to control the power on/off remotely, I am using this wireless power controller in the observatory. Using this I should be able to turn everything on/off remotely without having to get up on the roof

Also the insides of the observatory will be lit with this work light and red CFL spiral, in case I do need to go up there to tweak something


One final problem I need to figure out is the water tightness of the building for realistic rainy situations. The sides which have the rails should be fine:

But the front and back might not be:

One of these days I am going to climb up there with a garden hose and see where I need to do some work to block out rain. Most probably some plastic sheets will do the trick, but I need to test first. Of course I will have to do this before I put any equipment in there :)

All in all this project turned out pretty well.