FIG. 1 is a perspective view of a base for a luminary showing our new design. FIG. 2 is a front view of FIG. 1. FIG. 3 is a right side view of FIG. 1. FIG. 4 is a left side view of FIG. 1. FIG. 5 is a rear view of FIG. 1. FIG. 6 is a top view of FIG. 1; and, FIG. 7 is a bottom view of FIG. 1. The broken lines showing portions of the base for a luminary form no part of the claimed design.