Rayleigh optical depths that were calculated by Bucholtz represent an improvement over previous calculations (from 1.4% to 20%) because an updated depolarization factor that varied with the wavelength was used. These optical depths were obtained by integrating standard atmospheric model temperature and pressure profiles over height. This integration is a valid method for obtaining an estimate of the column density and therefore the Rayleigh optical depth, given that small errors (less than 0.7%) will be introduced because of quadrature and inaccuracies in any given model.