254mm. (True 10".) Parabolic Primary Mirrored Fully Coated Quartz SkyWatcher Dobsonian Reflector F/4.72:

This is Jules Vieira's 254mm. Aperture SkyWatcher Parabolic Mirror Reflector on a Dobsonian mount. This instrument is purely "Observational although through a Camcorder or Slow Shutter C.C.D. Camera can do the Planets and Some Very Bright Deep Sky, Orion M-42 can be Photographed using Slow Stacked Images of C.C.D. Animation 1/15th to 1/2 Second Shutter C.C.D. Imaging but that is all. It is a mostly observational instrument!