  We have been carrying out a program for over five years to observe transits
of selected exoplanets with 1-meter Turkish Telescope, T100 (Ba\c{s}t\"urk et
al. 2014, 2015), by making use of the well-established defocusing technique
(Southworth et al. 2009) to achieve high photometric precision. In this
contribution, we review the results of our observing program in timing
perspective. The basic idea behind defocusing technique is to have the
advantage of posing the detector for longer duration in the observations of
bright stars, otherwise observed within very short integration times. Then the
effect of the photon noise is diminished, which dominates in the short cadence
observations. Longer exposures also help in reducing the noise contribution of
the atmospheric scintillation. Noise contributions of the imperfect tracking
and flat-fielding are mitigated by integrating over a larger area on the
detector as well. Although fewer images can be acquired in a given time, we
argue that the timing precision is improved because of better photometric
precision. This contribution has been supported by T\"UB\.ITAK-3001 project
116F350.
