Several important turning points appeared in the personal life and scientific career of Zdeněk Kopal, every time, when he entered a new field of research. Four particular periods of his life will be commented in the present paper: the studies in Prague and early observations in the variable star programme of the Czech Astronomical Society; the first lectures on close binaries at Harvard; the intermezzo of lunar research; and the last period after 1989, when Zdeněk Kopal returned several times to Prague University.