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The Stargate Observatory

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photo of finished observatory

The Stargate Observatory
(A Small High School Gains a New Window on the Universe)

Text and pictures by Scott Azmus
Prepared for the web by Jonathan Blocher

One subject that the typical high-school student finds most intriguing is--no surprise--Astronomy. Yet most classes must content themselves with solar observing plus limited glimpses of the daytime moon and bright planets. Sadly, all the other wonders of the universe are often relegated to a planetarium program, video presentation, or textbook. Upon taking charge of the Astronomy program at Kenosha Wisconsin's Indian Trail Academy, I decided to sponsor an astronomy club. First order of business: convincing the school's advisory council that we needed our own observatory. In order to demonstrate the feasibility of a large student-built observatory, we first needed to plan and build a prototype.

Using ideas from various astronomy magazines and internet sites, our newly formed Space and Astronomy Club decided on a few must-have features. Kenosha is situated on Lake Michigan, midway between Milwaukee and Chicago. Light pollution is a major challenge (limiting magnitude ~5) and our winters can be COLD! We needed an observatory that was waterproof, snow proof, wind proof, and that would shield us from stray light. If possible, we were also looking for a design that would limit dewing and that could be rigged for full automation. While a roll-off roof would be easier to design, we needed a dome. Okay, so how big?

While the school's observatory would have to hold at least twenty students, the prototype only needed room for four or five. One club member had a brainstorm. While looking at the horizon through our tripod-mounted NexStar 11, she walked a full circle as another student marked the radius of her path. We added some comfort room and decided on a dome diameter of eight feet.

The pier, deck, and walls
We used ordinary hand tools, a good electric drill, and the very best jigsaw we could buy. That's an important note. Good tools. Even though we used three-quarter inch, exterior-grade plywood for the flooring and all dome arcs, we never broke a single jigsaw blade.

We obtained a permit and broke ground in early July. Club members helped clear an area eight foot square for the deck and took turns in the "pit:" an 18-inch diameter hole, four feet deep for the telescope's pier footing. Unable to find Sonotube of the correct diameter, we cut and duct-taped two 12-inch tubes to size. We hand-mixed twenty bags of concrete, added lengths of reinforcement bar, and poured the pier and eight deck footings. Although we were still waiting for our Astropier, the folks at LeSueur were kind enough to send the J-bolt assembly on ahead. We forced the bolts into the concrete, leveled them, and covered the pier to allow the concrete to cure. When installing the deck, we left a one-inch gap around the pier to totally isolate the telescope from its surrounding structure. While this was a novel idea for most students, a few simple demonstrations quickly proved the worth of such a simple feature. Moments after the pier arrived, we installed the telescope and enjoyed our first, seriously steady views!

The observatory has eight, four-foot walls, sized to allow observation of the local horizon. We framed two walls for ventilation windows, one for the door, and altered one wall to include an outer, shingled extension for a desk and shelves. We had to design, build, and mortis our own door. Mortising? Framing? Cost Analysis? Shingling? Details, details ... and yet, definitely some of the more important things our students picked up throughout the building process.

The Dome
Our plan required arcs and rings of several diameters, width, and thickness. The wall ring would be a double lamination, with an outer radius of 3'9" and a width of four inches. The dome base ring (three layers of plywood) was an even four feet in radius, again with a four-inch width. (The overlap would later aid in the installation of weather skirts.)

The main slit arches, dome ribs, and shutter arcs each also had their own radii, width, and thickness. Altogether, we cut a total of 98 four-foot arcs. These were laminated, glued, and screwed to form rings of appropriate diameter. We then cut the arcs to length and prepared to assemble the dome. Using a homemade trammel to scribe full-sized plans on our shop floor was an enormous aid in visualizing what we were trying to accomplish. The dome framework went together quite smoothly. Where the ribs met at odd angles, we elected to join them with hinges. I didn't think this would work, but it really turned out to be the way to go! The slit opening is over 33 inches wide and extends well beyond zenith. Not including the main slit arcs, there are six sets of support ribs.

Covering our poor, naked skeleton of a dome was the most tedious part of the entire operation. We used clear plastic to make the gore patterns and cut each gore from sanded 1/8-inch Masonite. Joining and securing the gores turned out to be a trial, as the plastic must have stretched as we stapled it to the dome frame. Fortunately, our plans carried a generous "tolerance" range and we were able to fine-tune each gore upon installation. Once the gores were on, we caulked each seam and added lengths of pine trim for added protection. After allowing the caulk to dry, we threw on several coats of primer and painted the dome interior a very dark, flat black. In order to prevent summer overheating, we used aluminum paint on the dome's outer surface. It looks like a "real" observatory and the paint matched our aluminum-sheet weather skirts.

Almost Done!
Seduced by the call of jambalaya and beer (it's a Wisconsin thing), several teachers dropped by to raise the dome. Although many of our club members are juniors and seniors, liability issues prevented any of them from being in on the big lift. Okay, okay: we didn't want them to know about the free food! The dome now rides on eight three-inch wheels, each capable of supporting 110 pounds. Four lateral guide wheels keep the dome to the "curved and narrow," and both shutters roll on a pair of tracks fashioned from a donated bed frame.

We elected to cover the upper tracks to prevent ice accumulation, but to leave the lower tracks open for fear that any added extension might pose a collision risk on a dark night. While they still pose a hazard, red "blinkies" alert approaching visitors to the shifting position of the lower track rail. We installed the door, wired the electrical service, added a set of heavy-weather tie-downs, and arranged our final inspection with the city of Kenosha. First light came just in time for Halloween.

While not drawing a dime of school district funds, our "Stargate Observatory" cost less than $800, took only a few weekends to build, and looks capable of enduring for some time. We are spending a lot more time under the stars and our science program now boasts deep-sky observing and basic astrophotography. We hope to obtain funding for a larger observatory (the "Rising Star" Observatory) sometime down the road and fully expect it to become a community effort as well as a community resource.

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