CCD V-band observations and archival O-C estimates are presented for the 4.
237 day Cepheid V1726 Cyg, which is a member of the open cluster C2128+488
(Anon. Platais), and the data are analyzed in conjunction with other availa
ble photometric data in order to study the star's period variations. An O-C
analysis of the data yields of following improved ephemeris for the variab
le, HJD(max) = 2,444,020.5892 + 4.2369334E + 2.044 x 10(-8)E(2), which impl
ies that the period of V1726 Cyg is increasing at a rate of +0.304 +/- 0.02
6 s yr(-1), consistent with a star in the third crossing of the instability
strip provided that it is pulsating in the first-overtone, rather than fun
damental, mode. Overtone pulsation for V1726 Cyg is also indicated by its l
ow amplitude, sinusoidal light curve, and derived Fourier parameters, despi
te reservations about the significance of the latter. No evidence is found
for random cycle-to-cycle variations in period for V1726 Cyg.