We present optical observations of a sample of 57 spiral galaxies and describe the procedures followed to reduce the data. We have obtained images in the...

From Hα images of a carefully selected sample of 57 relatively large, Northern spiral galaxies with low inclination, we study the distribution of the Hα...

The discovery of structure in the 5 minute oscillations of the sun, integrated over the full disk, was reported by Claverie et al. (1979). This paper presents...

We analyse the stellar content of almost 300deg^2 of the sky close to the Galactic plane by directly comparing the predictions of the SKY model (Cohen and...

Context. Abell 1995 is a puzzling galaxy cluster hosting a powerful radio halo, but it has not yet been recognized as a obvious cluster merger, as usually...

We present results of the inversion of spatially averaged Stokes I and V profiles emerging from plage regions near disk center. The observations analyzed in...

Context. Light bridges (LBs) are elongated structures with enhanced intensity embedded in sunspot umbra and pores. Aims: We studied the properties of a sample...

The discrete structure in the 5 min velocity oscillations of the solar surface has been confirmed by a re-analysis of data obtained between 1976 and 1979, and...

We present estimates for the size and the logarithmic slope of the disk temperature profile of the lensed quasar Q2237+0305, independent of the component...