Average atmospheric transmission function T(λ) as evaluated during full Moon just after the eclipse supposed to be similar to the one during the eclipse observations. The dashed line shows a transmission model (Hayes & Latham 1975), which includes both Rayleigh diffusion and aerosols (optical depth of 0.035 at 5320 Å typical for clear OHP nights). The experimental evaluation was normalized in order to match the model at our reference wavelength λ₀ = 4530 Å (see Sect. 5). O₂ as well as H₂O absorption bands are clearly seen. Note that the match with the model is good except for the central region from 5000 to 6700 Å, where a clear additional absorption is detected. This is the Chappuis band from ozone (noted O₃), not included in the model calculation.