The yoke of an alt-az telescope should provide a stiff interface between the azimuth journal and the tube of the telescope. The stiffness of the yoke affects the performance of the telescope servosystem and its mass has an important contribution on the total weight of the telescope. Based on the design of the yoke of the GTC 10m telescope, a new

EMIR is the NIR multi-object imager and spectrograph for the GTC (Gran Telescopio Canarias). The instrument ADR (Advanced Design Review) was held successfully in March 2006. During the AD phase, a number of mechanical concepts were tested on development prototypes to ensure the feasibility of the PDR proposed designs. This presentation contains an

A model for diffusion-controlled spherical particle growth is presented and solved numerically, showing how, on cooling at sufficient rate from a given fraction solid, growth velocity first increases, and then decreases rapidly when solute fields of adjacent particles overlap. An approximate analytical solution for the spherical particle growth

We report on optical spectroscopy of Swift J1933.9+3258 (=1RXS J193347.6+325422). This X-ray source has recently been classified as a likely radio-quiet AGN on the basis of its broad-band (radio, optical, UV, X-ray) properties (Grupe et al. 2006, ATel #859). In order to confirm its nature, a single 7-min spectrum of the optical counterpart was

We report on the spectroscopic confirmation of four recent optical nova candidates in M31 using the 2.2 m telescope and the Calar Alto Faint Object Spectrograph CAFOS at CAHA on Calar Alto, Spain. The spectra covered the range 400-850 nm (G-200), 490-780 nm (G-100) and 320-580 nm (B-100). The outburst of the apparent nova M31N 2006-06a (RA=00:43:11

Las estructuras de bajo brillo superficial detectadas en las galaxia enanas del Grupo Local y en sus proximidades, son estructuras extendidas que representan un registro fssil del pasado evolutivo de las galaxias. Su composicisn estelar es el objeto de analisis de esta Tesis. En ella se han estudiado dos galaxias de diferente morfologma. La primera