An algorithm is developed and tested for the problem posed by photomet
ric observations of the bulge of the Milky Way. The latter subtends a
non-trivial solid angle on the sky, and we show that this permits inve
rsion of the projected brightness distribution under the assumption th
at the bulge has three orthogonal mirror planes of specified orientati
on. A serious error in the assumed orientation of the mirror planes sh
ould be detectable.