Left: spatial variation of the measured ellipticities of stars that are selected for PSF modeling from Subaru observations. The orientation and length of the “whiskers” represent the direction and magnitude of shape distortion by the atmosphere and telescope. The Subaru PSF varies across the field of view, as well as between component frames. Right: modeled spatial variation of the Subaru PSF. The PSF is modeled for each component frame of the mosaic image and accumulated into a final PSF. The red line represents a 5% shear from circular. Comparison of the two figures shows the agreement between the measured stellar ellipticity and the corresponding PSF model for stars.