Calculated and reference opacities of astrophysical dust with CO ice and ice mixtures as a function of the wavelength. The dotted lines labelled with OH94 refer to bare grains and ice mixtures by Ossenkopf & Henning (1994), the dashed lines with BP98 to CO ice by Baratta & Palumbo (1998), and the solid lines to the CO data by the present work. The value V indicates the volume ratio of refractory core to ice mantle, for which we follow Ossenkopf & Henning (1994), where V = 0 (black) is the bare grain, V = 0.5 (blue) thin ice, and V = 4.5 (orange) thick ice. See text for additional details.