Figure 1: New Observatory Dome

Background:

The entire project took about 3 weeks to complete and actually was not as much work as I thought it would be. The total material cost is estimated to be about $500.00.

Construction:

Like any good project of this complexity, I started off with plans which you can click on below:

• Dome Plans

Once I had a good set of drawings, I could proceed on to the next step - building the frame of the observatory.

The existing base ring of the "Hexadome" is 90-inches in diameter and consisted of six nicely constructed pieces. Because of this I decided to make the dome base exactly the same size (the skirt would be out a futher 1/4-inch in radius). This choice of donme diamter meant I could "copy" one of these existing pieces with a flush cut bit and a router. The double-ring base, and ribs for the gords are all this diameter.

Figure 2: A Router bit that can be used for copying existing patterns

The next step is to trace out a pattern of the various pieces on plywood, using one of the old pieces as a template. Then I cut these pieces out with a jig saw, being careful to cut about an 1/8-inch on the outside of the pattern.

Figure 3: Tracing out patterns

The extra material will then be removed, using the router and the original piece as a guide as shown in figure 4 below.

Figure 4: Trimming the excess material with the router will produce an exact copy of the orignal piece

Figure 5: Twelve identical Pieces

The main ribs and arcs used in the slit covers were of a different diameter than the rest of the dome. In this case I cut out a master with a radius jig attached to my router. After the master was made, I could again use the same process as above to copy the rest.

Figure 6: Cutting a master arc of a different radius

The first piece I tackled was the base ring. It consists of two 90-inch diameter rings spaced apart 5.5-inches. I chose this over a single ring because it would provide greater stability, It would better support the skirt and it also provided me with 12 cubby holes to place stuff in while I am in the dome.

Figure 7: The Completed Base Ring

The next piece I tackled was the main slit ribs. This consisted of two layers of 1/2-inch thick plywood as shown in figure 8 below.

Figure 8: The Main Ribs in place

After that all that was required was to install the remaining ribs. The best way to do this is install the quarter ribs first. (I didn't do this and I had to do a bit of rework). The ribs are attached to the main slit with hinges (for the ones at an angle) and anfgle brackets. This is an idea that I picked up from Michael Cook's observatory.

Figure 9: Completed frame

Figure 10: Details on how the ribs are attached to the main ribs.

Once the frame was finished the next step was to cut out the gords. This is definitely a two person job (or even 3). Two of us held the 1/8-inch masonite sheets to the curve we wanted, and a third person traced it out. Than I added 1/2-inch (half the thickness of the ribs) to the traced pattern and cut it out. This technique worked well and I only had to redo one gord. These gords were then nailed to the frame using galvanized spiral nails. The final touch up was to nail plastic quarter-round to cover the seams. This provided a nice surface to caulk (for waterproofing) and it also hid a multitude of sins.

Figure 11: Covered frame with caulked seams.

After applying three coats of exterior paint (1 coat primer and 2 coats exterior paint) The dome was ready to be installed. Three of us lifted the dome to the base and placed it on top of the rollers. Then I nailed on the inner skirt. This consisted of 1/4-inch masonite (painted) which served as a surface for the lateral rollers to bear on, keeping the dome centred. Over of this skirt, a strip of vinyl siding was added to keep the weather out and make everything look neat.

Figure 12: Painted

Figure 13: Inside view of dome with my 8" LX-10

Surprising to me, the wood (mainly sheets of 1/8-inch masonite and 1/2-plywood) was only about a third of the cost. Most of the money went into "little things" like paint, trim, caulking and hardware. You can do most of the work by yourself with a few good tools (primarily a jigsaw and router), but some aspects will require help from others (i.e., tracing out the gords and lifting the dome in place).

I would highly recommend pursuing such a project. The three weeks of hard work will reward you for decades of use. Details of the dome construction will be published on my web site www.oocities.org/va3ngc in the near future. If you want to know more or would like to have a tour of the new observatory, please e-mail me.