Observatory Construction Photos (long)
Calculating Gore ShapeOther than the telescope, this observatory has been my most useful piece of equipment. I decided a home built dome would be the best design for my purposes. While saving thousands of dollars building it myself, the dome shape proved to be an inefficient use of materials compared to the square or rectangular shape of a rolloff observatory, in that we laminated material only to turn around and cut away a portion as scrap. However, if I had to do it again, I would build no other design.
The observatory was built to accommodate the Meade LX200 telescope. I initially set the telescope up, at a comfortable viewing height, in the garage. I added all the accessories, such as guidescope and dew shield and cut a profile of the dome out of cardboard to comfortably fit the azimuth and declination slewing of the telescope. An eight foot diameter dome, seven feet high seemed just right. So I built a ten foot diameter dome, eight feet high to accommodate a larger telescope in the future as the universe is expanding. --That one didn't work on my wife either. The dome aperture is three feet wide. This allows for well over an hours viewing or imaging before the dome needs to be turned. I decided to have the whole observatory turn so I could come and go through the door way with out turning the top back to the door or crawling over the wall when imaging. I estimate the total weight of the observatory at 6-700 pounds. My initial wheels were rubber and I was surprised at the amount of effort it took to get the observatory turning. These wheels were replaced with phenolic wheels and I can now easily turn the dome from a sitting position with one hand.
The shutter was built in two section. The lower section can be raised to make a doorway for access during the day or setting up in the evening. Both sections can be rolled well past the zenith for viewing or the lower section can be left closed, making an effective light barrier for any source below 20 degrees above the horizon. With the permanent setup I can powerup and be viewing or imaging with a correctly polar aligned telescope in five minutes.
Other than the mathematics required to calculate the shape of the gores, construction of the observatory was simple. A scrap, chip board base was laid on the floor of the garage, on which I centered a jig holding my router. All the pieces and parts, circles and semi-circles were cut, primed, and painted. The vertical walled base was built separate from the domed top for easier moving to the final site. Site work included building a short wall to provide a level spot (I have to make sure I don't become disoriented each time I walk out of the dome at night and fall off the wall), placing eight 6" concrete piers to support the turning wheels, and adding the telescope pier. One hundred ten volt electricity was buried to the dome and control cables were buried, in pipe, back to the house for remote control from my desktop computer. The most expensive part was the turning ring. I purchased 2" channel iron, the channel facing down, bent in a perfect circle, the same diameter as the dome, from a business supplying material to the ship building industry in Seattle, Washington. I also bought a second ring, bent from 2" flat bar, with the flat side up. Eight 3" diameter rubber wheels were welded to the flat ring so they appeared to be setting upside down. In this position I did not have to worry about dirt or rocks causing problems when turning the dome. The channel iron ring was set on these wheels which created a self centering turning design. The dome wall was bolted to flanges welded to the turning ring and the domed upper section was screwed and sealed with caulking to the wall. Several coats of paint were applied and the observatory was ready for use. Total construction time was approximately three months.
My LX200 is permanently mounted on a pier made from 6" steel tubing concreted approximately six feet in the ground. Additional concrete was poured around the steel pipe so the diameter of the finished pier is 16-17". A 1/2" steel plate is welded to the top of the pipe. This plate is tapped for four 3/8" bolts at each corner. A second 1/2" plate sits on top of the first and both are drilled for the main bolt that holds the superwedge as well as the three smaller bolts in the slot of the wedge. The four bolts tapped in the bottom plate are used to level the top plate should any shifting occur in the pier. I added an oblong serving tray between the pier and wedge for cigars, margaritas and eyepieces. The floor is separate from the pier and is designed like a deck so air can freely circulate from the bottom up. The dome seems to remain at ambient temperature at all times. I later added a piece of carpet so I could retrieve dropped screws etc. and has cushioned an eyepiece or two. Electricity and control cables are attached, out of the way, on the side of the pier.
I use 12 volt power for red lights in the dome. A RV battery sets on the base of the wall and is wired three way to the front and back of the dome so I don't have to get up to turn the lights on or off if needed. It was also the only way I could see how to have lights and not trip over or tangle up cord as the dome turned around.