Abstract: The open cluster M39 was observed by the new 1-m telescope at Weihai Observatory, Shandong University in the night of Oct. 7, 2009. While observing, a Johnson I-type filter was used and the CCD was imaged in two orthogonal orientations, and thus 30 frames of images were delivered. After the CCD images were measured by 2-D Gaussian fit so as to obtain the star pixel positions, a number of constant plate models were attempted to solve the difference between observed positions and computed ones for each star. Our reduction of the observations showed that proper motions of the latest USNO UCAC3 star catalogue were explicitly not accurate. By contrast, those of the Platais's catalogue were found much better. This observations partly confirmed the errors in the proper motions of UCAC3 recently discovered by Roeser et al. Experiments have also shown that the best precision for a suitable bright star was about 4~5 milli-arcsec. It was believed that this new telescope could be used for high precision astrometry.