Blue stragglers in open clusters III. NGC 7789

We performed for the first time a detailed LTE spectroscopic study of a sam ple of blue straggler stars in the moderately old open cluster NGC 7789. Fo r eight stars the parameters and abundances of several elements were determ ined. The cluster members: show a remarkable surface magnesium deficiency w hich is quite unusual for late B - early A stars. Iron and titanium abundan ce are ill agreement with other photometric and spectroscopic estimates of the NGC 7789 metallicity. All the confirmed blue stragglers have rather low projected rotational velocities (with one exception for K88, v sin i = 80 km s(-1)).