Periodicities in the optical brightness variations of the intermediate polar TV Columbae.

We present extensive observations in the Walraven (VBLUW) photometric system of the intermediate polar TV Col over the period 1985-1988. We find, apart from the photometric variations at the three previously known periods, long-term brightness changes between groups of observations of up to {DELTA}B_J_~0.4mag. During the periods of highest mean brightness the source shows 1-2mag outbursts, of which we detected four during our observations. No photometric variations are detected at the X-ray pulse period, or at its orbital or 5.2hr period sidebands. We derived a new ephemeris for the orbital period, and we determined arrival times of maximum light at the 5.2hr and 4day photometric periods. We are unable, using the arrival times from our own data and those listed in the literature for the 5.2hr light curve, to determine any constant-period ephemeris to fit all the observations. We suggest that the 5.2hr period is in fact not stable and can vary non-monotonically. Because the 4 day period is the beat period between the orbital period and the 5.2hr period, this also applies to the variations at this period. We investigate the changes in the optical light curve as a function of the 4 day cycle and discuss their cause.