In a homogeneous magnetoplasma the refractive index is given by the dispersion relation, which assumes that the angle between the wave normal and the superimposed magnetic field is known. But a radio signal travels along a path known as a “ray” whose direction is in general different from the wave normal, and in many problems it is the ray direction that is known and the wave normal direction is at first unknown. In a previous paper, for a plasma in which the only effective carriers are electrons, a formula was given for finding the refractive indices when the ray direction is given. In this paper the formula is extended to allow for the presence of heavy ions. It is an equation of degree six whose solutions are associated with six different waves, although not all of them are necessarily excited by a given source. The properties of the equation are illustrated by discussion of its solutions at cut-off frequencies and resonance frequencies, and by showing its connection with resonance cones, Storey cones, and window points. A specific example of a plasma containing protons and He + ions is studied as an illustration.