2 Observations and data reduction

The spectroscopic observations of BK Psc were obtained during four observing runs:

1) 2.2 m-FOCES 1999/07
This run took place on 24-29 July 1999 using the 2.2 m telescope at the German Spanish Astronomical Observatory (CAHA) (Almería, Spain). The Fibre Optics Cassegrain Echelle Spectrograph (FOCES) (Pfeiffer et al. 1998) was used with a 2048x2048 (15$\mu$) LORAL$\char93$11i CCD detector. The wavelength range covers from 3910 to 9075 Å in 84 orders. The reciprocal dispersion ranges from 0.03 to 0.07 Å/pixel and the spectral resolution, determined as the full width at half maximum (FWHM)of the arc comparison lines, ranges from 0.09 to 0.26 Å.

2) INT-MUSICOS 2000/08
This run was done on 11-14 August 2000, with the 2.5 m Isaac Newton telescope (INT) at the Observatorio del Roque de Los Muchachos (La Palma, Spain) using the ESA MUSICOS Spectrograph. This is a fibre-fed cross-dispersed echelle spectrograph (Baudrand & Bohm 1992) and developed as a part of MUlti-SIte COntinuous Spectroscopy (MUSICOS) project. During this observing run, a 2148x4148 pixel EEV10a (EEV4280) CCD detector was used. The wavelength range covers from 4000 to 10 000 Å in 87 orders. The reciprocal dispersion ranges from 0.03 to 0.08 Å/pixel and the spectral resolution (FWHM) from 0.06 to 0.24 Å.

3) NOT-SOFIN 2000/11
This run took place on 6-9 November 2000 using the 2.56 m Nordic Optical Telescope (NOT). The Soviet Finnish High Resolution Echelle Spectrograph (SOFIN) was used with an echelle grating (79 grooves/mm), camera ASTROMED-3200 and a 1152x298 pixel EEV P88100 CCD detector. The wavelength range covers from 3900 to 8400 Å in 37 orders. The reciprocal dispersion ranges from 0.06 to 0.14 Å/pixel and the spectral resolution (FWHM) from 0.15 to 0.42 Å.

4) 2.2 m-FOCES 2001/09
The last run took place on 21-24 September 2001 using the 2.2 m telescope at the German Spanish Astronomical Observatory (CAHA) (Almería, Spain). In this run, the FOCES spectrograph (Pfeiffer et al. 1998) was used with a $2048\times 2048$ (24$\mu$) SITE$\char93$1d CCD detector. The wavelength range covers from 3450 to 10 700 Å in 112 orders. The reciprocal dispersion ranges from 0.04 to 0.13 Å/pixel and the spectral resolution (FWHM) ranges from 0.1 to 0.34 Å.

In Table 1 we give the observing log. For each observation we list date (Day), universal time (UT), exposure time (Exp), and the signal to noise ratio (S/N) measured in the H$\alpha$ line region.

The spectra have been extracted using the standard reduction procedures in the IRAF package. The wavelength calibration was obtained by taking spectra of a Th-Ar lamp. Finally, the spectra have been normalized by a polynomial fit to the observed continuum.