The spectroscopic observations of inactive stars presented here were carried out during several observing seasons, from 1988 to 1995, within a program devoted to the study of optical activity indicators in chromospherically active single and binary stars (Montes et al. 1994, 1995a-d, 1996a,b; Martín & Montes 1997). The high and mid-resolution spectra were obtained with three telescopes: the 2.2 m Telescope at the German Spanish Astronomical Observatory (CAHA) in Calar Alto (Almería, Spain), using a Coudé spectrograph with the f/3 camera, the Isaac Newton Telescope (INT) and the William Herschel Telescope (WHT) located at the Observatorio del Roque de Los Muchachos (La Palma, Spain), using the Intermediate Dispersion Spectrograph (IDS) with the cameras 500 and 235 at the INT and the ISIS double arm spectrograph at the WHT.
The different observational campaigns, the telescope and detector
used and the spectral region observed in each season
are given in Tables 1 (click here) and 2 (click here).
We also give for each spectral region the
wavelength range (
) covered
and the spectral resolution (
) achieved.
The spectra have been extracted using the standard reduction procedures in the MIDAS and IRAF packages (bias subtraction, flat-field division, optimal extraction of the spectrum, and wavelength calibration using arc lamps). More details of the observations and data reduction for the different observational seasons from 1988 to 1995 can be found in Fernández-Figueroa et al. (1994); Martín et al. (1994) and Montes et al. (1995a-d, 1996b).
The high-resolution observations cover four spectral ranges:
(3970.07 Å) and in some cases
the 
(3889 Å) and 
(3835 Å) Balmer lines.
(6562.8 Å) line region that in some observational seasons
also include the Li I 6708 Å line and the
Fe I 6663 Å, Fe I 6678 Å and Ca I 6718 Å
lines used in rotational velocity determinations
(Huisong & Xuefu 1987).
(4861.32 Å) line region.
(5876 Å) line region
that also includes the Na I 
(5895.92 Å)
and 
(5889.95 Å) lines.
We measured the resolution of our spectra using emission lines of arc lamps
taken on the same nights. Typically the full width at
half maximum (FWHM) was two pixels.
The spectral resolution (
)
achieved ranges between 0.2 and 0.5 Å
(
, 25000-10000) depending on the observational
season (see Table 1 (click here)).
The mid-resolution observations (
between 0.8 and 3 Å)
cover, in some cases, the 
line region
and in other cases the 
and
Na I 
and 
line region (see Table 2 (click here)).
In the 
, 
, and Na I 
, 
,
and He I 
line regions the spectra have been normalized
by fitting a polynome to the observed continuum.
However, in the Ca II H & K line region
it is very difficult to fit a continuum so the spectra have been normalized to
the measured flux in a 1 Å window centered at 3950.5 Å.
This reference point at 3950.5 Å is not a real continuum, but it is a
relatively line-free region that could be used as a pseudo-continuum to
normalize all the Ca II H & K spectra and that has been used by
Pasquini et al. (1988)
to develop a calibration procedure for converting the
observed line fluxes into absolute surface fluxes.
In the case of the mid-resolution spectra of M stars it is also
difficult to establish a continuum, due to the presence of strong
molecular bands, so we have normalized these spectra by means of
the pseudo-continuum regions used by Martín et al. (1996) located
at 6525-6550, 7030-7050, and 7540-7580. At lower wavelengths we
included other two regions near 5795 and 6150 Å.
We plot the spectra normalized to those points in Fig. 6 (click here).
However, in the database available by ftp or WWW, we have divided the spectra
only by the average continuum level in the region 
in
order to preserve the observed shape.