In this talk I propose first of all to briefly review the basic survey method for discovery of far away PNs and comment on the specific problem of contamination of the surveys by background emission-line galaxies and by H II regions that belong to the surveyed galaxy. As illustration I expect to show PNs in NGC 300, a nearby late spiral, and in two flattened elliptical galaxies: NGC 4697, at a distance of about 10 Mpc, and NGC 1344 in Fornax.

The discovered PNs can be used in several ways. The initial motivation was distance determination using the PN luminosity function (PNLF) method of Ciardullo and Jacoby. Nowadays the emphasis is shifting towards measuring PN radial velocities, which can provide important information about angular momentum and dark matter distribution in spheroidal galaxies.

I will describe an efficient method for radial velocity determination using spectrographs like FORS at the VLT and FOCAS at the Subaru telescope. Finally, I will report on our project of PN abundances in the elliptical galaxy NGC 4697 (total exposure time: 3 VLT nights plus one Keck night) and on what we can infer about metallicity and metallicity gradient in this galaxy (a collaboration with Daniel Thomas and Roberto Saglia, among others). The results we have obtained have a possible incidence on the small but persistent systematic discrepancy between PNLF distances and Surface Brightness Fluctuations (SBF) distances.