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Description
We present echelle spectroscopy in the 3500-10300{AA} range of the Hourglass Nebula, which is embedded in the Galactic H II region M8. The data were obtained using the 2.1m telescope at Observatorio Astronomico Nacional in San Pedro Mqrtir, Baja California. We have measured the intensities of 274 emission lines, in particular 88 permitted lines of C^+^, N^0^, N^+^, O^0^, O^+^, Ne^0^, S^0^, S^+^, Si^0^, Si^+^, and Si^++^, some of them produced by recombination only and others mainly by fluorescence. We have determined electron temperatures and densities using different line intensity ratios. We derive the He^+^, C^++^, O^+^, and O^++^ ionic abundances as well as - for the first time in a nebular object - the total O abundance from recombination lines; these nebular values are independent of the temperature structure of the nebula. We have also derived abundances from collisionally excited lines for a large number of ions and elements; these abundances do depend on the temperature structure. Accurate t^2^ values have been derived by comparing the C^++^, O^+^, and O^++^ ionic abundances obtained making use of both collisionally excited lines and recombination lines. A comparison of the solar, Orion Nebula, and M8 chemical abundances is made.
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