We present a new estimate of the mass of the Milky Way, making use of a large sample of 955 field horizontal-branch (FHB) stars from the Early Data Release of the Sloan Digital Sky Survey. This sample of stars has been classified on the basis of an automated analysis approach, in combination with other methods, in order to obtain estimates of the

We have imaged ˜ 1 deg2 in the V-band in the direction of the Hercules cluster (Abell 2151). The data are used to compute, for the first time, the luminosity function (LF) of galaxies in the cluster down to the dwarf regime (Mlim ˜ -13.85 ). The global LF is well described by a Schechter function (Schechter 1976) with best-fit parameters α = -1.30

We are conducting a study on the energetics and dynamical evolution of the final stages of intermediate and massive stars. Our project includes the study of the ionization structure of the haloes of MSPNe and WRNe, and the detection of a possible shock-heated gas component. We present here the set of observations so far obtained, and preliminary

The DIMM is a widely accepted and often used instrument for seeing measurements. Nevertheless, its incorrect use may give rise to errors in seeing values. A detailed analysis of the parameters involved in the seeing calculation is being undertaken and the effect of saturation of the spots in particular is analyzed in this contribution. Our results

Site selection is, no doubt, one of the most important preliminary studies in any telescope project since the image quality of the telescope will be limited by the site quality. Traditionally, geotechnical studies have had relatively little importance, normally being carried out once the site was already selected. However, with the increase of the

The Gran Telescopio Canarias (GTC) is, being assembled at the Observatorio del Roque de los Muchachos (ORM) in the island of La Palma. First light is expected for early 2005 with the first science observations late in 2005. The GTC, being a segmented primary mirror telescope, could be employed for testing several technological aspects relevant to