Line-of-sight velocities (V_LSR) of NH₃ (J,K) = (1, 1) (squares) and HC₃N J = 2–1 (triangles) along the main diagonal cuts towards the molecular cores L1512 and L1498 measured in 2010 (dashed lines) and in 2011 (solid lines) at the Effelsberg 100-m radio telescope. The half-power beam width at 23 GHz is 40′′ (50′′ at 18 GHz), the backend is the fast Fourier-transform spectrometer (FFTS) with a channel separation Δ_ch = 0.015 km s^-1 (0.020 km s^-1 at 18 GHz).