Offsets along the R.A. and decl. axis relative to J2000 ﹩(\alpha ,\delta )=(1{3}^{{\rm{h}}}0{3}^{{\rm{m}}}13\mathop{.}\limits^{{\rm{s}}}867940(53),-10^\circ 5{1}^{{\prime} }17\mathop{.}\limits^{^{\prime\prime} }12905(18))﹩ for J1303−1051 (top panel) and ﹩(\alpha ,\delta )=(1{2}^{{\rm{h}}}5{4}^{{\rm{m}}}52\mathop{.}\limits^{{\rm{s}}}25525,-10^\circ 1{4}^{{\prime} }50\mathop{.}\limits^{^{\prime\prime} }634)﹩ for SN 2012au (bottom panel). We plot the total uncertainties, which include both statistical and systematic contributions induced by phase referencing to the phase calibrator, J1305−1033 (L. Y. Petrov & Y. Y. Kovalev 2025). In the top panel, we overplot the 1σ-localization contour of the check source J1303−1051 from P. Charlot et al. (2020), highlighting consistency in our repeated phase-referenced measurements. The one observation inconsistent with the remaining observations of J1303–1051 was omitted when measuring the proper motion of SN 2012au. Measurements performed at the K band (22 and 24 GHz) are indicated as squares, and those at the C-band (5 GHz) as circles. The color scale of each data point is scaled relative to the original explosion date.