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Materials
The beauty of the Dobsonian telescope is its simplicity. The tube is usually made from a sonotube-̵1;a cardboard tube used for pouring concrete pillars and posts. You can get one from the lumber yard. If you are building a scope with a 6-inch mirror, you'd buy an 8-inch sonotube and cut it to the correct length. The base is made of a single sheet of plywood as thin as 1/4 inch, though 1/2 inch plywood is better for ease of assembly. The base is a plywood disk with an old phonograph record or sheet of Teflon attached to the top. The base of the telescope support is a rectangular plywood box with an old phonograph record or Teflon sheet attached to the bottom. You'll need Teflon or velvet strips for the vertical mount, too. For the scope you'll need a telescope mirror and mirror mount (although Dobson used a wooden shingle that blew off a house to mount his first mirror). You'll need eyepieces, an eyepiece focusing mount, a spider and mirror for a tube the size of the mirror you are using. You'll need a spotting scope to help point the scope in the right direction. The rest of what you need is screws and bolts, glue and plywood cutouts as well as Dobson's detailed plans or a variant of his basic design.
How Dobsonians Work
The Dobson mount has two moving parts. The circular base sits flat on the ground. A rectangular hollow plywood pillar-shaped box sits atop the base held in place by a single bolt. Teflon or old phonograph records sit between the pillar and base, allowing the pillar to rotate smoothly, but still maintain sufficient friction to hold the tube when focusing on a star. The top of the pillar has a U-shape cut along two sides. The telescope tube is mounted in a wooden open-ended box with wooden disks mounted on the sides of the box like ears. The box sits on top of the pillar, the ears nested in the U-shaped seat. The inside edge of the U-shape and the outside of the disk ears are lined with velvet or Teflon. The tube tips up and down smoothly, yet sits firmly for focusing. The two movements, up and down and round and round allow the tube to point at any object in the sky and move easily to track the object. The scope is a Newtonian with the eyepiece at the high end of the tube and the mirror at the base.