An early VLBI observation of the quasar 3C 286

Using the hybrid mapping technique based on self-calibration and CLEAN algorithms, we reprocessed the data of an early (1976) VLBI observation (by T. J. Pearson et al.) of quasar 3C 286 at 18 cm, and obtained a high quality CLEAN map. We can get more information from the new map than from the old one. Four Gaussian models were used to fit the calibrated UV data. We found that the central bright region could be resolved into two compact components. This was in accordance with the later higher angular resolution VLBI observations. Comparing with the results of other VLBI observations, the distance between these two components was found to vary not only with frequency at a given time, but also with time at a fixed frequency.