Abstract:
To search for optical variability on a wide range of timescales, we have carried out photometric
monitoring of a dozen blazars. CCD magnitudes in B, V, R and I pass-bands were determined for > 10,000
new optical observations from 300 nights made during 2011 – 2016, with an average length of ∼ 4 h each, using
seven optical telescopes: four in Bulgaria, one in Greece, and two in India. We measured multiband optical flux
and colour variations on diverse timescales. Blazar variability studies helped us in understanding their nature
and extreme conditions within the emission region. To explain possible physical causes of the observed spectral
variability, we also investigated spectral energy distributions using B, V, R, I, J and K pass-band data.
