We know about 300 ZZ Ceti stars currently, nonetheless, only a limited number of pulsation modes are known for most of them, usually the results of the short discovery runs. This is mainly because of the faintness of these objects, and because of the limited access of ground-based telescopes large enough for follow-up observations. However, we need more pulsation modes for asteroseismology for sufficient constraints on the physical parameters of the stars. Fortunately, there are several ways to collect more information on pulsating white dwarf stars. International observing campaigns, space-based time-series photometry of white dwarf variables, or long-term single-site ground-based observations of selected targets proved already that we can extract sufficient number of pulsation frequencies for performing asteroseismic modelling.

In my talk, I present examples for these latter cases: I introduce some results obtained on ZZ Ceti stars utilising TESS (Transiting Exoplanet Survey Satellite) measurements, and the results of the ground-based observations performed at the mountain station of Konkoly Observatory on two additional ZZ Ceti targets. In this latter case, one of the stars was discovered as a new variable by Konkoly observations, while the other one was observed both from the ground and by the TESS space telescope, respectively.