The Hemispherical Dome
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The hemispherical dome does have many advantages over other shapes. Not the least of these is its attractiveness: a well designed and finished dome reminds us of Mt. Palomar and other great observatories. These aesthetic considerations are important: the owner and the neighbors will be looking at this structure for a long time! A well designed dome also offers superb wind and stray light protection. And, with a generous shutter opening, a dome gives a wide field of view of the sky.

Designing a dome observatory appears easy because it is a simple shape, based on the simplest figure, the circle. But, as is often the case, life is not that easy, so let's look at some of the design challenges for a hemispherical dome.

Many people are not aware that a circle is one of the weakest structures: it can take very large forces if they are uniformly applied, but is amazingly easy to distort if non-uniform forces are applied. The "equator" of a hemispherical dome shares this property: if not designed properly, it can deform and become hard to turn when the user applies force to turn the dome. To obtain a properly rigid dome, one must reinforce the equator, and indeed, all the related arcs in the dome. In the HOME-DOME, this strength is provided by wide internal flanges on all circular arcs.

Figure 1.6 CIRCLE STRENGTH

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