PSR B2021+51 positions and 1 σ error ellipses, with a superposed curve representing the modeled pulsar track across the plane of the sky, as calculated from the estimated parameters in Table 2. The origin represents the calculated pulsar position at the reference epoch (1992.723). A cross denotes the calculated pulsar position at the epoch of each observing session (see Table 1). North is up, and east is to the left; the direction of motion is toward the north‐northwest.