Improved non-LTE line formation calculations for hydrogen in O-stars are presented. The calculations are carried out by means of the method recently developed by Werner and Husfeld (1985) and use an extensive hydrogen model atom with 10 non-LTE levels and 55 transitions. For most of the transitions Stark-broadening is included in the statistical

Ground-based multichannel photometry of integral sunlight has been obtained at Izaña (Tenerife) during three months in 1984 with a photometer built at ESTEC. Power spectra of solar irradiance variations of individual days show power in the 5 min band just above noise at a level comparable to the one found from the SMM data (Woodard and Hudson, 1983

The published J, H, and K band photometry of Frogel et al. (1983) for a sample of over 350 red giants in 33 galactic globular clusters, which covers the complete range of metallicities found in globular clusters, is used to derive a set of empirical relations which allow to predict the intrinsic colors of Population II giants as a function of

Preliminary results of a search for the variation of the solar granulation properties with the heliographic latitude are presented. Within errors, no changes are found in the power spectra and sizes between N-S and E-W scans.

Results are presented from a search for variations in solar granulation properties with heliographic latitudes. Photographs taken in the summers of 1985 and 1986 are used to study the power spectra in the direction perpendicular to the solar radius. It is found that there are no important differences in the power spectra obtained for positions

An analysis of the center to limb variation of the geometrical properties of spots has been carried out. It has revealed that spots do not have a symmetrical behaviour with respect to the centre of solar disk. Thus, the Wilson effect is not zero at δ = 0°, but at δ ≡ 45°W. Moreover, the inverse Wilson effect is the general rule in that interval