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Dobsonian Telescopes: the most aperture for your dollar!
A Dobsonian telescope is a Newtonian reflector mounted on a simple yet stable alt-azimuth (lazy Susan style) mount. These telescopes are named for their designer, John Dobson, who sought to build a low cost large aperture telescope. No other design has had a greater impact on amateur astronomy in the past half century. Dobsonian telescopes are popular because they offer the most available aperture for the dollar. Virtually all amateur telescopes over eleven inches in aperture seen at star parties are Dobsonians. Wikipedia has a fine article on the history and origins of the Dobsonian Telescope.
Dobsonian Telescope: Solid vs. Truss Tube
Two types of Dobsonian telescope are commonly available. Dobsonians with solid tubes are popular in apertures up to ten inches. The Orion SkyQuest Classic models are examples of this type. Above about twelve inches in aperture a solid tube becomes a bit too unwieldy to handle. This gives rise to the truss tube design, which is assembled in the field prior to use. The Meade LightBridge series are examples of a truss tube Dobsonian. Virtually all amateur telescopes over fourteen inches of aperture are truss tube Dobsonians. The collapsible Dobsonian is an interesting variation of the truss tube design. These telescopes provide most of the benefits of a truss tube system without all of the field assembly requirements. The Sky-Watcher Collapsible Dobsonians are an example of this concept.
