A Dobsonian or Dob is a type of Newtonian reflector used on an inexpensive plywood or fiberboard alt-azimuth mount. The scope is moved manually from object to object as there are no slow motion controls or drive for the simple mount. Plastic Teflon bearings in the trunnions allow smooth and easy telescope motion. Oriented almost exclusively towards visual rather than photographic use, Dobs are usually large aperture, fast f/ratio scopes.
Because of their simplicity, easy-to-use "light bucket" Dobs are an economical way to get into large-aperture astronomy at a relatively low cost.