The forthcoming proper motions of more than 100.000 stars provided by Hipparcos with an accuracy of better than 2 mas/a will be an important tool for the study of stellar kinematics and dynamics. However the Hipparcos satellite was only able to provide relative proper motion data. Therefore the proper motions of the Hipparcos satellite had to be calibrated with other techniques (e.g. Froeschlé & Kovalevsky 1982). As already proposed by Brosche (1980) one promising method for the calibration of absolute proper motions is the use of extragalactic objects on photographic plates. While first results for the calibration of proper motions were already published (e.g. Brosche & Geffert 1981; Brosche et al. 1991a; Geffert et al. 1993), we present here absolute proper motions of 48 stars, which were also measured by the Hipparcos satellite. Our data have been recently used for a complete Hipparcos link solution of all Bonn fields (Tucholke et al. 1997) and for the final link of the Hipparcos proper motion system (Kovalevsky et al. 1997).