The highest gain antenna in the world today is the 50 foot parabolic reflector built for the Naval Research Laboratory for operation at wavelengths as short as 8 mm. A description of this precision antenna, which is used for research in radio astronomy, is presented. The mechanical aspects of the dish are given primary consideration. Fabrication procedures, design considerations and a description of the unique surface machining apparatus are treated -- these techniques yielding a reflector with an over-all surface accuracy of

inch. A mention is made of a few of the recent advances in radio astronomy made at NRL through the use of the Big Dish -- testifying to the successful completion of the project.