Progenitor identification of PTF12os found by registering 8 ground-based NTT/EFOSC i-band images of PTF12os to a stacked pre-explosion HST ACS F814W image. The field of view shown here is . North is up and east is to the left. The white circles show the average position of the centroid of PTF12os after image registration with a radius reflecting the statistical error from 7 image registrations. The smaller circle represents a 2σ uncertainty and the larger circle represents a 5σ uncertainty. The 2σ uncertainty is only shown in the zoomed inset. The pink circles indicate the centroid of the possible progenitor measured in the HST image, with a radius representing the 2σ uncertainty in its centroid.