Searching for optical flickering in 3 symbiotic stars

We observed the symbiotic systems NQ Gem, ZZ CMi and BF Cyg in the period January -- March 2011 with the 60-cm telescope of the Rozhen National Astronomical Observatory in B-band. In our monitoring these systems did not show flickering. However, the systems ZZ CMi and BF Cyg demonstrated low (below 0.01 mag), but statistically significant intra-night parabolic trend of variability, while NQ Gem did not.