1996-2009 optical photometric monitoring for 3C 66A

It has been monitored since 1996 December 11. In the present work, we show its optical light curves during the period of 1996 December 11-2009 December 28.

From our observations, we found that the largest variations in the V, R, and I bands are {Delta}V=1.840+/-0.065, {Delta}R=1.898+/-0.069 mag, and {Delta}I=1.659+/-0.047 mag, respectively. Intra-day variabilities are found in the three bands: in the V band, an A=17.7% brightness increase over {Delta}T=47.5 minutes on JD 2455119, and an A=46.27% brightness increase over {Delta}T=271.4 minutes on JD 2454816; in the R band, an A=47.09% brightness increase over {Delta}T=23.18 minutes on JD 2454004, and an A=38.11% brightness increase over {Delta}T=87.98 minutes on JD 2453995; and in the I band, an A=13.2% brightness decrease over {Delta}T=38.44 minutes on JD 2453995, and an A=92.8% brightness decrease over {Delta}T=344.02 minutes on JD 2454818.