A medical probe includes a tubular distal end section, which is configured to be inserted into a cavity of a patient, and includes (a) a visually guiding object disposed over a perimeter of the distal end section, and (b) a magnetic field sensor including two sensor coils aligned non-parallel with each other, the sensor attached to the distal end section, and having: (i) a first axis of symmetry, of one of the coils, which is aligned perpendicular to a central longitudinal axis of the distal end section, and (ii) a second axis of symmetry, of the remaining coil, which is aligned perpendicular to the central longitudinal axis of the distal end section and not parallel to the first axis of symmetry.