Dark matter and doppler effect

Hi everybody,

The calculations of the normal rotation period of the galaxies we observe depends on their observed mass, but it also depends on the doppler effect from their recession. The more they speed away from us, the more their period is stretched. When we calculate this period, thus when we calculate their rotational speed, we have to include doppler effect in the calculations, which increases that speed. Has anybody thought of not including the doppler effect in the calculations? If not, can somebody do these calculations for a couple of galaxies and tell me if their rotational speed is still too fast to account for their observable mass?