Rosseland mean opacities (RMOs) and radiative accelerations (RAs) for arbitrary chemical mixtures are computed online directly from the Opacity Project (OP) monochromatic opacities. The mixture is specified by the hydrogen (X) and metal (Z) mass-fractions (X+Y+Z=1) and its metal fractional composition (default = S92 of [4]). For detailed documentation please check the reference list below. The OP opacities were refined in December 2004 to include inner-shell contributions [10], and the OPserver software upgraded in June 2006 to enable local installations and library linking. The complete OPCD_3.0 package (data, codes and instructions) to compute locally RMOs and RAs [11] and to install the OPserver can also be downloaded from the OP home page.

1. OPCD_2.0 reference manual
2. Fitting and smoothing of opacity data
   Seaton M.J., 1993, MNRAS 265, L25. Abstract
3. Opacities for stellar envelopes
   Seaton M.J., Yu Yan, Mihalas D., Pradhan A.K., 1994, MNRAS 266, 805. Abstract
4. Interpolations of Rosseland-mean opacities for variable X and Z
   Seaton M.J., 1996, MNRAS 279, 95. Abstract
5. Radiative accelerations in stellar envelopes
   Seaton M.J., 1997, MNRAS 289, 700. Abstract
6. Diffusion of iron-group elements in the envelopes of HgMn stars
   Seaton M.J., 1999, MNRAS 307, 1008. Abstract
7. On the importance of inner-shell transitions for opacity calculations
   Badnell N.R., Seaton M.J., 2003, J. Phys. B 36, 4367. Abstract
8. A comparison of Rosseland-mean opacities from OP and OPAL
   Seaton M.J., Badnell, N.R., 2004, MNRAS 354, 457. Abstract
9. Up-dated opacities from the Opacity Project
   Badnell N.R., Bautista M.A., Butler K., Delahaye F., Mendoza C., Palmeri P., Zeippen C.J., Seaton M.J., 2005, MNRAS 360, 458. Abstract
10. OP data on CD for mean opacities and radiative accelerations
    Seaton M.J., 2005, MNRAS 362, L1. Abstract