H beta photometry of southern CP2 stars: is the uvby beta luminosity calibration also valid for peculiar stars?

We present H beta photometry of 233 southern CP2 stars (covering the magnet ic Ap stars according to the definition by Preston 1974) brighter than V < 8.5 mag from the list of Bidelman & MacConnell(1973). Absolute magnitudes derived from this photometry together with already exis ting u upsilon by photometry is confronted with Hipparcos results available for a common subset of 152 stars. In order to compare peculiar with normal stars, we identified a sample of 1 147 normal B to F-type stars using their published u upsilon by beta and Hi pparcos data. For our analysis we divide both samples into three temperature as well as t wo Hipparcos parallax accuracy groups. The error distribution of both sampl es proved to be statistically comparable. As a result the absolute magnitudes for the B-type CP2 stars show up to be significantly too bright by an average of 0.5 mag using the actual photomet ric calibration. On the other hand, the photometric absolute magnitudes for cool A to F-type CP2 stars are up to three magnitudes fainter as compared to Hipparcos.