MMA Memo 119

We consider the optimum north-south elongation for the Millimeter Array A con guration and interferometric arrays in general. The optimum elongation depends primarily on the observational requirements of the array, with a very weak dependance on the latitude. Assuming that the Millimeter Array A con guration will be used primarily for long integrations, we nd that the optimum north-south axis ratio is 1.1 for the latitudes of both Mauna Kea (19:8 N) and South Baldy (34 N). Finally, we present two options for locating an array of this size on the proposed Mauna Kea site.