  Homeotropic Nematic Liquid Crystal heated from above present convective
Rayleigh-Benard instability for applied thermal gradients greater than
$\Delta$Tc. This threshold increase with the intensity of applied external
magnetic field parallel to the initial molecular orientation (vertical). We
studied the different patterns which exist near to and away from the threshold,
such as hexagons and squares, and the transitions between them. The study of
patterns evolution away the threshold shows coexistence between patterns and a
global system dynamics. Also we studied how this general dynamics change with
the inclination of the cell, where for very small angles (1 degree) the
hexagons and squares are transformed into rolls.
