  The bright Nova Cygni 1975 is a rare nova on a magnetic white dwarf (WD).
Later it was found to be an asynchronous polar, now called V1500 Cyg. Our
multisite photometric campaign occurring 40 years post eruption covered
26-nights (2015-2017). The reflection effect from the heated donor has
decreased, but still dominates the op- tical radiation with an amplitude
~1^m.5. The 0^m.3 residual reveals cyclotron emission and ellipsoidal
variations. Mean brightness modulation from night-to-night is used to measure
the 9.6-d spin-orbit beat period that is due to changing accretion geometry
including magnetic pole-switching of the flow. By subtracting the orbital and
beat frequencies, spin-phase dependent light curves are obtained. The amplitude
and profile of the WD spin light curves track the cyclotron emitting accretion
regions on the WD and they vary systematically with beat phase. A weak
intermittent signal at 0.137613-d is likely the spin period, which is 1.73(1)
min shorter than the orbital period. The O-C diagram of light curve maxima
displays phase jumps every one-half beat period, a characteristic of
asynchronous polars. The first jump we interpret as pole switching between
regions separated by 180 deg. Then the spot drifts during ~0.1 beat phase
before undergoing a second phase jump between spots separated by less than 180
deg. We trace the cooling of the still hot WD as revealed by the irradiated
companion. The post nova evolution and spin-orbit asynchronism of V1500 Cyg
continues to be a powerful laboratory for accretion flows onto magnetic white
dwarfs.
