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 \pm 4 Myr and a distance of roughly 3 kpc for this cluster .
The proper motion study identifies 77 stars of V = 14.5 \mbox { 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 .