2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/14573We 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=-1.80.9 pages, 11 figures, accepted for publication in Astronomy & Astrophysics, Main JournalAstrophysicstext