Abstract:
We have monitored some of the BL Lac objects, such as OJ287, Mrk 421, Mrk 501 etc from Mt Abu Infrared Observatory, using optical photopolarimeter, CCD and NICMOS-3 IR array mounted at the Cassegrain focus of the 1.2 m telescope. The data obtained indicate existence of variability at various time scales. Some of the results on OJ 287 and Mrk 421 are presented here.
