  We use scanning gate microscopy to map out the trajectories of ballistic
carriers in high-mobility graphene encapsulated by hexagonal boron nitride and
subject to a weak magnetic field. We employ a magnetic focusing geometry to
image carriers that emerge ballistically from an injector, follow a cyclotron
path due to the Lorentz force from an applied magnetic field, and land on an
adjacent collector probe. The local electric field generated by the scanning
tip in the vicinity of the carriers deflects their trajectories, modifying the
proportion of carriers focused into the collector. By measuring the voltage at
the collector while scanning the tip, we are able to obtain images with arcs
that are consistent with the expected cyclotron motion. We also demonstrate
that the tip can be used to redirect misaligned carriers back to the collector.
