Variation in the Lyα/Lyβ irradiance ratio versus the Lyα irradiance from a subset of EGS-SEE measurements taken in the 2002–2010 year range (crosses represent the observation and the solid line is a least squares polynomial fit). For comparison purposes, we also show the result of a rocket flight, obtained in February 18, 1978 to calibrate the OSO8/LPSP spectrometer (Lemaire et al. 1978), as a large, unfilled circle.