We present new transit light curves for planets in six extrasolar planetary
systems. They were acquired with 0.4-2.2 m telescopes located in west Asia,
Europe, and South America. When combined with literature data, they allowed us
to redetermine system parameters in a homogeneous way. Our results for
individual systems are in agreement with values reported in previous studies.
We refined transit ephemerides and reduced uncertainties of orbital periods by
a factor between 2 and 7. No sign of any variations in transit times was
detected for the planets studied.Comment: Submitted to Acta Astronomic