  The presence of elongations in active region (AR) polarities, called magnetic
tongues, are mostly visible during their emergence phase. AR tilts have been
measured thoroughly using long-term white-light (WL) databases, sometimes
combined with magnetic field information. Since the influence of magnetic
tongues on WL tilt measurements has not been taken into account before, we aim
to investigate their role in tilt-angle values and to compare them with those
derived from LOS magnetograms. We apply four methods to compute the tilt angle
of generally bipolar ARs: one applies the k-means algorithm to WL data, a
second one includes the magnetic field sign of the polarities to WL data, and a
third one uses the magnetic flux-weighted center of each polarity. The tilt
values computed in any of these ways are affected by the presence of magnetic
tongues. Therefore, we apply the newly developed Core Field Fit Estimator
(CoFFE) method to separate the magnetic flux in the tongues from that in the AR
core. We compare the four computed tilt-angle values, as well as these with the
ones reported in long-term WL databases. For ARs with low magnetic flux tongues
the different methods report consistent tilt-angle values. But for ARs with
high flux tongues there are noticeable discrepancies between all methods
indicating that magnetic tongues affect differently WL and magnetic data.
However, in general, CoFFE achieves a better estimation of the main bipole tilt
because it removes both the effect of tongues as well as the emergence of
secondary bipoles when it occurs in between the main bipole magnetic
polarities.
