OP monochromatic cross-sections lgσ (in atomic units) vs. for lgN_e = 16 and lgT = 4.8,5.0,5.2, and 5.3. The yellow lines show the total opacity produced by all elements considered in the OP project, the black lines display opacity caused by H, He, Fe, and σ_e, while the violet lines correspond to Fe. The Rosseland-mean weighting function is also plotted as smooth lines. The brown line in the two lowest panels correspond to H, He, and σ_e.