for HCG 88a (reproduced in Fig. 2) shows asymmetries with disagreement between the two sides of the galaxy (a bifurcation of the curve at a radius of 10 arcsec). We overplot on Fig. 2 the Fabry-Perot data for HCG 88a, with values restricted to a narrow cone around the galaxy major axis (to mimic a slit), using the particular values of center, inclination and position angle derived by R1991 photometrically. Inspecting the figure we see that for radii larger than 10 arcsec, there is good agreement between the slit-spectroscopy and Fabry-Perot data, if the photometrically derived center, inclination and position angle are used. However, the overall shape of the curve changes when such parameters are derived from the velocity map and a large sector of the galaxy is averaged (the resulting rotation curve is shown in Plana et al. 2003 and in Fig. 1). In particular, if the kinematic parameters are used and velocities over a large sector of the galaxies are averaged, the bifurcation present in Fig. 2, at r $\sim$ 10 arcsec, disappears, and the galaxy has normal kinematics, with both sides of the curve matching.

In order to understand the magnitude of the variations of the parameters 