This paper presents the results of an investigation of the quiet Sun's magnetic field based on high-resolution infrared spectropolarimetric observations obtained with the Tenerife Infrared Polarimeter (TIP) at the German VTT of the Observatorio del Teide. We observed two very quiet regions at disc centre. The seeing was exceptionally good during

The seemingly un-magnetized part of the solar surface is not really un-magnetized. It is occupied by magnetic structures producing low polarization which, therefore, escape detection in traditional measurements. Since most of the solar surface belongs to this category, the quiet Sun magnetic fields can easily carry most of the magnetic flux and

We determine the physical conditions in NGC 6543, obtaining two different estimates of the electron temperature (T[e]) and one estimate of the electron density (N[e]). The electron temperature is computed by means of the [O III] ratio lambda 5007/ lambda 4363, and of the diagnostic diagram combining lambda 5007 to the [O III] infrared lines 52 mu

VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template frame was necessary to obtain reliable photometry. We used a template frame of NGC 3190 taken during the course of our galaxy imaging project, fortunately, just a few days before SN 2002bo was

We report differential I-band and J-band photometry of S Ori 45, a cool (spectral type M8.5), young (1-8 Myr) brown dwarf of the sigma Orionis cluster with a likely mass estimated at around 20 times the mass of Jupiter. We detect variability (amplitudes ranging from 34 to 81 mmag) and observe a modulation at a period of 2.5-3.6 h in both optical

We discuss the effects of collisional enhancement of Balmer lines on the determination of the primordial helium abundance. To this aim, we present a photoionization model of the metal-poor extragalactic H 0 region SBS 0335-052. We show that the derived helium abundance (Y) of this H 0 region depends on the amount of collisional excitation affecting