Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands e-mail: email@example.com
2 SRON Laboratory for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
3 Laboratory for Astronomy and Solar Physics, Code 681, Goddard Space Flight Center MD, USA
Accepted: 11 March 2005
The ISO and IUE spectra of the elliptical nebulae NGC 2022, NGC 6818 and IC 4191 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous determinations. A discussion is also given of the exciting stars of the nebulae, and possible evolutionary effects.
Key words: ISM: abundances / ISM: planetary nebulae: individual: NGC 2022 / ISM: planetary nebulae: individual: NGC 6818 / ISM: planetary nebulae: individual: IC 4191
© ESO, 2005