In the last two decades, part of the observational time at Bulgarian National Astronomical Observatory (BNAO) Rozhen was dedicated to asteroid observations. Even though during 2021, we had limited time, we collected enough information to proceed with differential photometry on many asteroids. Using a combination of lightcurves of an asteroid, gained from observations at several oppositions, we were able to determine precise synodic periods, and through analysis of the different lightcurves, we can give predictions about their preliminary shape. In this work, we will present the process for synodic period determination for 418 Alemannia, 339 Dorothea, 901 Brunsia, and 2650 Elinor. Moreover, using the characteristics of the lightcurves, we will calculate the ratio between the axis of the asteroid and give first assumptions about its shape.