Originally posted by: Chandraketu
Dunno whether Rahu/Ketu are counted as one or two.
They are counted as two. In astrological calculations, they are the two lunar nodes. To find lunar nodes, assume a sphere of any size with Earth at the center. In reference of the Earth, find a plane which contains the orbit of the Moon. This plane intersects the sphere in a circle. Again in Earth's frame, consider the plane, which contains the orbit of the Sun. This plane also intersects the sphere in a circle.
So you have two circles. These two circles meet each other at two points. These two points are Rahu and Ketu.