Mie calculations of the mass required to produce the observed radiance in the data from May 14. The lines correspond to different refractive indices for the dust particles. Solid line: n = 1.55 + 0.1i, dashed: n = 1.8 + 0.01i, dot-dash: n = 1.8 + 0.4i, dot-dot-dash: n = 2.0 + 0.1i. The size distribution cut-offs at 1 mm. If larger particles were to be included in the calculation, the roll-over seen at low values of b would not occur. The diamond indicates a similar calculation for data from May 5. Here, the radiance from the nucleus (obtained prior to the outburst) was subtracted from the data to leave the residual from the outburst itself. The radiance was converted to a mass at b = 4. If the calculation were extended over all size distributions, the curve shape would be identical to those shown.