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Dobsonian

In astronomy the Dobsonian is a type of telescope mounting that became popular in the 1980s for its extreme simplicity and rugged construction. Invented by John Dobson, it is a basic altitude/azimuth mount that does not follow the motion of the stars. It is therefore less technically advanced than most other mounts, but tends to be very well balanced and have smooth operation, as well as being very compact and portable.

The Dobsonian mount consists of three major parts. Azimuth (side-to-side) motion is provided by a turntable, on top of which sits a large box. Into the upper sides of the box are cut two semi-circular cutouts. Two disks are fixed to either side of the telescope at the balance point, and fit into the cutouts on the box to provide altitude (up-and-down) motion. The various bearing points are lined with several pieces of teflon (typically, although felt is also sometimes used) as a bearing surface.

The entire mount is quite small in comparison to typical star-tracking systems, and can be easily transported. This has made it a favourite of amature astronomers because it can be carried to star parties in the back of a small car and set up in moments. The result has been a fixation with ever-larger telescopes, which would otherwise require huge "traditional" mounts. Whereas a 8" Newtonian would be considered large 30 years ago, today 16" systems are common, and huge 32" systems not all that rare.