Ground-based Ring-effect measurements with the OSIRIS development model

The Ring effect is measured using the UV-visible spectrometer (similar to1 nm spectral resolution) of OSIRIS, the optical spectrograph and infrared imaging system. The observed filling in of Ca(II) H and K (similar to395 nm), the two largest Fraunhofer lines in the solar spectrum, are compared with the filling in simulated with a new model that includes rotational Raman scattering (RRS) by N-2 and O-2. The filling in is (1.06 +/- 0.60)% at Ca(II) K and (1.40 +/- 0.50)%, at Ca(II) H for blue-sky observations at a solar zenith angle of 37degrees. The measured filling in agrees with the modelled filling in within the uncertainties.