Highly popular with amateur astronomers, the Dobsonian telescope took to the scene in the 1970s when creator John Dobson decided he wanted to expose the general public to the power of large scopes. Prior to this, amateur astronomy was dominated by small telescopes bought commercially. Dobson's goal was to build telescopes impressive in size for everyone at a low cost, thus widening the number of people able to experience the wonders of the science.
The type of telescope was a basic Newtonian reflector scope and the size was: big. This in itself was not a problem, but the mount needed to support it was. The cost would be in the thousands of dollars, which was not very practical for the amateur astronomer.
So Dobson decided to make a simple, yet radical, change. He stepped away from the traditional tripod (pier) mount and instead, replaced it with a box-like structure with a flat bottom. Called an altitude-azimuth box, its flat foundation enabled the telescope's weight to be distributed across the box's entire surface. Meanwhile, Teflon bearings enabled mobility.
As for the cost, problem solved. The mount could be made out of any number of inexpensive materials, including everyday plywood. Of course, manufacturers scooped up the idea for themselves and today it's very easy to find a Dobsonian telescope ("Dobs") on the commercial market. It's also still a snap to create a homemade alt-azimuth box yourself. As a result, the Dobsonian-style scope is probably the most common design among amateurs and is seen all over star parties.
There are some compromises made when using a Dobs. One is the fact that because of its mounting, it cannot move in the same way that stars do; and two, charting must be done manually or by memorization unless modifications are made (which would lead to added cost). However, these considerations aside, the Dobsonian telescope is still a strong recommendation for any beginner astronomer.
Finally, one other development born out of the Dobsonian design is the truss Dob, where the tube of the telescope is removed and instead replaced by a skeletal structure of smaller tubes. The focuser cage and mirror box are connected by said tubes, and the overall weight of the device is reduced considerably. Anything above a 12" aperture (100+ pounds) would require a truss for practical mobility.
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