Rotation curve of NGC 3521. Panela: Line-of-sight Hα velocity (km s⁻¹) field in sky coordinates (arcsec). The values of the V_los are colour-coded. The circle shows the kinematic centre of the galaxy; the line indicates the position of the major kinematic axis of the galaxy; the ellipse is the optical radius. Panelb: Rotation curve of NGC 3521. The grey points mark the individual fibres used in the determination of the final rotation curve. The red circles denote the mean values of the rotation velocity in bins of 5 arcsec in the radius, and the bars show the scatter in rotation velocities about the mean value in the bins. Panelc: Comparison of the obtained rotation curve with those from the literature. The red points show the rotation curve obtained here from the Hα velocity field; the green dashed line denotes the rotation curve determined by Daigle et al. (2006) from the Hα velocity field; the blue dotted line marks the rotation curve derived by de Blok et al. (2008) from the H I velocity field; and the dark solid line is the rotation curve derived by Lang et al. (2020) from the CO velocity field.