Oxygen and helium abundances in Galactic HII regions -: I.: Observations

Absolute integrated line fluxes of H II regions have been measured using a Fabry-Perot spectrophotometer. We describe the observations and calibration procedures. Fluxes are given for 36 H II regions with Galactocentric distances ranging from 6.6 to 17.7 kpc. Several emission lines have been measured, mainly [O II] lambda lambda 3726 and 3629, H beta, [O III] lambda 5007, He I lambda 5876 and H alpha. The very faint [O III] lambda 4363 line has been measured in six regions, allowing a direct determination of the electron temperature. New photometric distances have been derived based on data from the literature. A discussion of these results in terms of extinction, electron density and temperature, and oxygen and helium abundances is given in Paper II.