Long-term blind spectropolarimetric monitoring can be ineffective in obtaining the final result — establishing the magnitude and topology of a stellar magnetic field. The high quality photometric data from TESS makes it possible to search for periodicity at different time intervals. For those who perform direct magnetic field measurements, this provides a reliable base for deep studying the magnetic field across the HR diagram, including its variability associated with different phenomena (rotation, pulsations, shock waves, active regions etc.). At the Crimean Astrophysical Observatory, high-accuracy measuring the magnetic field on non-degenerated stars at different evolution stages has been performed on a regular basis since 1987. For magnetic field calculation the Single Line technique based on Zeeman splitting in individual spectral lines has been developed. We will present our technical capabilities for spectropolarimetric observations, as well as some of our most significant results on stellar magnetism obtained earlier.

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