Parallax and proper motion fit for OH 231.8+4.2. For each plot, points with error bars are position measurements of the H₂O maser spot at V_LSR of 25.52 km s⁻¹ relative to the background quasar J0746–1555. Left panel: Motion of the maser on the sky. Middle panel: Change of position eastward (solid line) and northward (dashed line) as a function of time. The northward data have been shifted downward for clarity. Right panel: Same as the middle panel after removing the best-fitting linear proper motion.