  We attempt to measure the proper motions of two magnetars - the soft
gamma-ray repeater SGR 1900+14 and the anomalous X-ray pulsar 1E 2259+586 -
using two epochs of Chandra observations separated by ~5 yr. We perform
extensive tests using these data, archival data, and simulations to verify the
accuracy of our measurements and understand their limitations. We find 90%
upper limits on the proper motions of 54 mas/yr (SGR 1900+14) and 65 mas/yr (1E
2259+586), with the limits largely determined by the accuracy with which we
could register the two epochs of data and by the inherent uncertainties on
two-point proper motions. We translate the proper motions limits into limits on
the transverse velocity using distances, and find v_perp < 1300 km/s (SGR
1900+14, for a distance of 5 kpc) and v_perp < 930 km/s (1E 2259+586, for a
distance of 3 kpc) at 90% confidence; the range of possible distances for these
objects makes a wide range of velocities possible, but it seems that the
magnetars do not have uniformly high space velocities of > 3000 km/s.
Unfortunately, our proper motions also cannot significantly constrain the
previously proposed origins of these objects in nearby supernova remnants or
star clusters, limited as much by our ignorance of ages as by our proper
motions.
