Optical observations of planetary nebula candidates from the northern hemisphere^*

¹ European Southern Observatory, Casilla 19001, Santiago 19, Chile
² Kapteyn Astronomical Institute, P.O.Box 800, NL-9700 AV Groningen, The Netherlands
³ NOAO , P.O. Box 26732, Tucson, AZ 35726, U.S.A.

Send offprint request to: G.C. Van de Steene

Received: 17 May 1995
Accepted: 8 January 1996

Abstract

We present Hα+[N ii] images of 17 and low resolution spectra of 14 IRAS-selected planetary nebula candidates. The Hα+[N ii] images are presented as finding charts. Contour plots are shown for the resolved planetary nebulae. From these images accurate optical positions and mean optical angular diameters were determined. Optical spectra show that the IRAS-selected and radio detected planetary nebula candidates are indeed planetary nebulae. Three planetary nebula candidates, previously not detected in the radio continuum were seen in Hα. They are larger, low surface brightness planetary nebulae. Most of these IRAS planetary nebulae are heavily extinct, having an average A_V of 7 magnitudes. About half of the planetary nebulae seem to be of low excitation, having central stars with an effective temperature probably ~ 60.000 K or less.