In recent years, the capability to detect and analyse solar oscillation acoustic modes has greatly improved. The development of ground based networks like GONG or BiSON and the use of space platforms like SOHO has allowed us to study the structure and dynamics of the Sun with unprecedented precision.

We present quantitative analyses of 7 galactic O stars of spectral types from O3 to O6. By means of classical hydrostatic and planeparallel models we find the so-called He and Mass Discrepancies for a number of stars of our sample. We also prove the need of line-blocking for the correct reproduction of these spectra. For stars with effective

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We present very deep RIc photometry of the M35 open cluster. We have covered 30' \times 30', equivalent to about a fourth of the total area of the cluster. The data range from I_c=17.5 to 23.5 magnitudes, and the color interval is $0.5 \le (R-I)_c \le 2.5$. Roughly, these values correspond from $0.6 M_\odot$ to $0.1 M_\odot$ in the cases of members

The Gran Telescopio CANARIAS (GTC) is a high performance 10-m class telescope whose construction has been promoted by the IAC (Instituto de Astrofísica de Canarias). It will be installed at the Roque de los Muchachos Observatory (ORM), in the island of La Palma. First light is planned for end-2002. The key science drivers for the project are image

EMIR is a near-infrared (NIR) multi-object spectrograph (MOS) proposed for first-generation common user instrument of the Gran Telescopio Canarias GTC. It has three observing modes: imaging, multiobject spectroscopy and integral-field spectroscopy, in the NIR Z, J, H and K bands. The design uses cryogenic multislit masks to allow simultaneous