Proper motion study of the globular cluster M 92

We present proper motions for stars in the field of the galactic gIobular cluster NGC 6341 (M 92), This study continues the series of papers from the Bonn programme of globular cluster proper motions. Plates taken with the Bonn double refractor and the Rozhen observatory 2m Ritchey-Chretien telescope with a maximal epoch difference of 94 years were used. Relative proper motions for all well-measurable stars in the 1.5 degrees x 1.5 degrees field covered by the plates were derived. Median proper motion errors are 0.8 milliarcsec/year (mas/a) for stars brighter than about V = 16.7m. The cluster membership of W-bright and variable stars is discussed. The proper motions an compared with the accurate relative proper motions of Pees (1992) and with the absolute proper motions from Schmidt plates referred to galaxies of Scholz ct al. (1994). The latter comparison enables us to lie the proper motions of the stars and the mean proper motion of M 92 to an inertial system, This calibration has an uncertainty of about 1.0 mas/a. The absolute proper motions of Hipparcos stars in the field will be useful for the extragalactic calibration of the Hipparcos proper motion system. The data for 642 stars within 18.6' from the cluster centre is available via the CDS (Centre des Donnees Astronomiques Strasbourg) Data Centre.