By Gareth Branwyn, MAKE – March 08, 2010 at 06:00PM
Craig Smith, of Firefly Workshop, has been planning a home observatory and is working out the details of easily building a domed roof for it. He writes:
Anybody with a decent telescope knows that a telescope should be cool as the night air to prevent heat radiant distortion. Aside from keeping it out in an unheated shed yet still having to set it up, one will sometimes make an observatory of sorts. Many have built retractable roofed sheds and the like. But my mind kept working at a cheap lightweight dome roof built in the classic style. Anybody with basic carpentry skills can build a cylindrical wall structure or octagon walls, but the dome roof has always been a difficult and expensive build. Here’s my prototype made from cardboard, 1/6th scale.
A single 3/4″ sheet of 4′ X 8′ plywood, supplies the material for the framework. The circle makes the base, and circular cutouts outward from that make the frame ribs. Since there is some leftover waste, the framework will be lighter than the full sheet of plywood. But many little galvanized framing brackets used to fasten it together will add some weight, as well as the roofing material. A 24″ wide roll of galvanized flashing will be used to make the 10 roof pie-segments and the rear rectangular segment. Put on with small galvanized box nails, each pie panel will overlap the one next to it, sealed waterproof with silver flashing seal caulk during assembly.
The retractable watertight sky opening will be tricky. But if all else fails it could be made like a standard flat roof access door only curved. Standard flashing and roofing techniques are a must here to keep an expensive telescope safe and dry.
Have you ever built such a structure? Got any design input for Craig?
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