Chemically peculiar upper main-sequence stars in the Milky Wayand beyond

Delta-a photometry is a valuable and economical tool for detecting magnetic chemically peculiar stars, owing to their characteristic flux depression at 5200A. Our main focus of attention is to survey galactic open clusters in order to identify chemically peculiar cluster stars. Since open clusters offer the big advantage that parameters like age or distance can be determined rather accurately, one can thence trace relationships between such parameters and other properties. On the basis of about 80 open clusters covered so far with Delta-a photometry, we present a preliminary analysis that shows the evolution of magnetic chemically peculiar stars. Apart from the galactic representatives, Delta-a photometry has also been able to discover mCP stars in another environment: the Large Magellanic Cloud. This nearby galaxy exhibits properties that are different from those of the Milky Way, a factor which can also be invoked to investigate the conditions that favour the formation of chemically peculiar stars.