The optical warps of NGC 5907 is studied by means of CCD photometry, for the U and I filters, as well as for a narrow band filter centered at H-alpha. The present observations were extended out to about 380 arcsec in the NW side and out to about 348 arcsec in the SE side. The H I warps begin at these galactocentric radii, so that the optical ones

A popular description of the Titan Satellite of Saturn is given. Some recommendations for its observation are given. The space programs in view of its exploration are also described.

The paper presents simultaneous monitoring of the BL Lacertae object Markarian 501 obtained in the visible and near infrared using a double photometer system on the 1.5 m Carlos Sanchez Telescope situated in El Observatorio del Teide (Tenerife) and CCD photometry in U and B taken with the 1 m Jacobus Kapteyn Telescope of El Observatorio del Roque

The authors present preliminary results of an infrared monitoring program of selected blazars, conducted at the Carlos Sanches Telescope at Izana Observatory, Teneriffe. Eight blazars have been observed during three observing runs since August 1990. All observed blazars have shown variability.

The results of one night of observations corresponding to an intensive site assessment campaign, held at the Observatorio del Roque de los Muchachos (La Palma) on July 22 1990, are presented and discussed. The goal of the campaign was to evaluate the contribution of free atmosphere, boundary layer, surface layer and dome + mirror seeing to image

We report on intermediate-to-high resolution spectroscopy and standard broadband photometry of late-type visual companions to early-type stars. Our program stars are drawn from the sample of post-T-Tauri candidates studied by Lindroos (1986). Measurement of radial velocities and derivation of the surface abundances of lithium and heavier elements