Subarcsecond optical imaging of proto-planetary nebulae

Subarcsecond (0 ".75) V and I images have been obtained of 13 new proto-pla netary nebulae (PPNs). We find nine of them to be resolved, with sizes up t o 3 ", and two others to perhaps also be extended. Of the nine, four appear to be elliptical in shape. Thus an aspherical morphology is demonstrated t o commonly exist early in the transition between the asymptotic giant branc h and planetary nebula phases. The results of this larger observational stu dy, together with the previously published imaging studies, indicate that m ost PPNs are elliptical (or bipolar) in shape.