Statistics are presented covering 20 years of use of the 2.1m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, Baja California, Mexico. As in the previous compilation, the fractional number of nights with totally clear, partially clear and mostly cloudy skies were determined. The fraction of nights lost due to bad weather was

A 50 min time series of one-dimensional slit-spectrograms, taken in quiet sun at disk centre, observed at the German Vacuum Tower Telescope (Observatorio del Teide), was used to study the global and spatial variations of different line parameters. In order to determine the vertical structure of the photosphere two lines with well separated

A spectroscopic study of the Trapezium Cluster stars in the Orion Nebula is presented. We determine the stellar parameters of the two B0.5V stars theta(1}_{) Ori A and D. The variable spectral features of theta(1}_{) Ori C are studied, and some consequences on the modeling of the stellar atmosphere are considered.

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S5>~5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of

Only less than 150 Wolf-Rayet galaxies are actually known. Many of them are dwarf or irregular galaxies, and some show close companion objects. Peculiar morphological features, like mergers or tidal tails connecting small stellar aggregates, are found in many cases. Therefore, we think that interaction could be an important mechanism that triggers

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne V] 342.6 nm, the Bowen fluorescence line of O III at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as Hα, [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne V