In this contribution, the main characteristics of the=20 Tenerife Infrared Polarimeter (TIP), recently built at the Instituto de Astrofísica de Canarias, to be operated at the German Solar Telescopes (GCT and VTT) of the Observatorio del Teide (Tenerife) are presented. Especial emphasis is put on the modulation scheme, polarisation efficiencies

We present an estimate of the solar rotation rate near the surface (i.e., the outer 1%) based on rotational splittings estimated for high degree modes ( ) from the SOI/MDI dynamics program. We also present and discuss the nature and magnitude of systematic errors present in the evaluation of high degrees rotational splittings and their implication

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We have performed a detailed oxygen abundance analysis of 23 metal-poor (-3.0 [Fe/H] -0.3) unevolved halo stars and one giant through the OH bands in the near UV, using high-resolution echelle spectra. Oxygen is found to be overabundant with respect to iron in these stars, with the [O/Fe] ratio increasing from 0.6 to 1 between [Fe/H] = -1.5 and

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