Light curve of 28 Cyg observed with BTr (+) and UBr (°) in 2015 (top) and BTr in 2016 (bottom). Fitted constant-amplitude sine curves with frequencies 0.0508 c/d (2015) and 0.0496 c/d (2016) are overplotted in blue and trace the respective f_Δ32 (≈ f₃ − f₂). JD = Julian Date. The zero points of the magnitude scales are arbitrary. It should be noted that the difference in magnitude scale between 2015 and 2016. Fifty-seven BeSS spectra were obtained between mJD 632 and 733 (see Figs. 19 and 20).