  We present CCD photometry and a proper motion study of the young open star
cluster, NGC 581 (M 103). Fitting isochrones to the colour magnitude diagram,
we found an age of 16 +/- 4 Myr and a distance of roughly 3 kpc for this
cluster. The proper motion study identifies 77 stars of V=14.5 mag or brighter
to be cluster members. We combine membership determination by proper motions
and statistical field star subtraction to derive the IMF of the cluster and
find a quite steep slope of Gamma=-1.80.
