Proper Motion of the Crab Pulsar Revisited
  It has been suggested that the Crab pulsar's proper motion is well aligned with the symmetry axis of the pulsar wind nebula. We have re-visited this question, examining over 6 years of F547M WFPC2 chip 3 images to obtain a best-fit value of $\mu_\ast = 14.9 \pm 0.8$mas/yr at PA $278\arcdeg \pm 3\arcdeg$. At $26\arcdeg\pm 3\arcdeg$ to the nebula axis, this substantially relaxes constraints on the birth kick of this pulsar. Such misalignment allows the momentum to be imparted over $\sim$1s timescales. 
C.-Y. Ng and Roger W. Romani