  We report on photometric follow-up of the recently discovered transiting
planet WASP-1b. We observed two transits with the Wise Observatory 1m
telescope, and used a variant of the EBOP code together with the Sys-Rem
detrending approach to fit the light curve. Assuming a stellar mass of 1.15
M_sun, we derived a planetary radius of R_p = 1.40 +- 0.06 R_J and mass of M_p
= 0.87 +- 0.07 M_J. An uncertainty of 15% in the stellar mass results in an
additional systematic uncertainty of 5% in the planetary radius and of 10% in
planetary mass. Our observations yielded a slightly better ephemeris for the
center of the transit: T_c [HJD] = (2454013.3127 +- 0.0004) + N_tr * (2.51996
+- 0.00002). The new planet is an inflated, low-density planet, similar to
HAT-P-1b and HD209458b.
