Conclusions

• The absolute precision to which the pointing of array elements can be measured scales like the inverse cube of their diameter and the inverse square root of their number. Therefore larger antennas are favored.
• Frequent pointing calibration should be possible with the LSA/MMA antennas, in order to reach a pointing accuracy suitable for high dynamic range mosaics (0.3-0.5'', depending on the antenna size), provided the tracking is able to reach that accuracy. This could relax the need for pointing stability on time scales longer that 30 min.
• Measured on a 1 hour time scale, the pointing stability of the Plateau de Bure antennas is about /hour r.m.s. in low wind conditions (< 5m/s)
• On shorter time scales the specifications (0.7'' rms on each axis) seem well fulfilled; the accuracy is actually in azimuth.
• More measurements are needed in good seeing conditions (<0.5'') with strong sources to investigate the limiting performance of the tracking.