Observations and simulations of some divergent-light halos

We deal with some halos generated by the divergent light from a nearby source. After discussing how the divergent light transforms some halo features, we give an outline of a method of handling the simulation of a divergent-light halo. The simulation method is then successfully tested on some well-documented halo observations. We also present a "simulation atlas" that shows halos produced by crystals of different shapes and for different light-source elevations and distances between the observer and the light source. The simulation method also admits a three-dimensional visualization of the phenomena. (C) 2003 Optical Society of America.