Spectral subtraction example from PW And, a K2V star. The different spectra show chromospheric indicators in Ca II H and K (top panels), Hβ and Na I D₂ (middle panels), and Hα and Ca II IRT-a lines (bottom panels). Using FOCES provided spectra for each panel. Lower panel: observed target spectrum (blue) and synthetic spectrum (red), obtained from a reference star spectrum; upper panel: subtracted spectrum (green). In both panels, the vertical blue dashed lines mark the integration limits for the chromospheric excess emission EW determination.