Adaptive optics performance: the top panel shows the K-band Strehl ratio as a function of atmospheric seeing (at 500 nm). The Strehl ratio and seeing are derived from the wavefront residuals as observed with the wavefront sensor, and calibrated with K-band observations of the components of wide binary stars using the VLTI Infrared Image Sensor (IRIS, Gitton et al. 2004). The bottom panel shows the closed loop transfer function for Zernike modes up to order 44 as measured on the m_K = 6.5 mag star GC IRS 7. Both curves are representative for observations of bright objects with m_K ≲ 7 mag.