Planetary nebulae (PNe) have been used to trace the chemical evolution of galaxies, not only in the Milky Way (Esteban & Peimbert 1995 and references therein) but also in nearby galaxies (Dopita et al. 1997; Richer et al. 1999; Jacoby & Ciardullo 1999). Extragalactic PNe have also been used as secondary distance indicators by means of the planetary

The existence of an extended component of diffuse ionized gas (DIG) is a well-known property of spiral galaxies. The integrated ensuremath {{H}alpha } luminosity of the DIG is very high (accounting for ~ 50% of the total ensuremath {{H}alpha } emission in a galaxy), which makes it important to understand the origin of this diffuse component.

We have compared direct estimates of the ionizing photon flux from the stars observed within the H II region NGC 346 in the Small Magellanic Cloud with its observed H alpha luminosity using a series of photoionization models of the region. The tests were based on the use of the photoionization code Cloudy (Ferland 2000), aided by H, He, N, O, Ne, S

Available from the Minor Planet Center.

We conducted two multi-site campaigns for two previously poorly-studied rapidly oscillating Ap (roAp) stars, HD122970 and HD99563. In January-June 1998, we observed HD122970 with 7 telescopes at 6 observatories and obtained 119 hr of data. We decided to organise a larger campaign for the same star in the year 2001 (5 telescopes at 4 observatories

The magnetic properties of the quiet Sun are investigated using a novel inversion code, FATIMA, based on the Principal Component Analysis of the observed Stokes profiles. The stability and relatively low noise sensitivity of this inversion procedure allows for the systematic inversion of large data sets with a very weak polarization signal. Its