The Strömgren 
photometric system is widely accepted as
one of the astrophysically most well calibrated photometric
systems available. Numerous 
, 
, [Me/H], microturbulence and
interstellar reddening calibrations have been published through
the years, covering all together wide ranges in spectral type and
luminosity class. Its carefully selected narrow-intermediate
wavelength bands make the system suitable for detailed
investigations of single stars, including variables, binaries and
clusters, as well as for studies of the structure and evolution
of the Milky Way and nearby galaxies.
With present days extended use of CCD's accurate
photometry can be obtained for quite faint objects, but one of
the new challenges is to bring the data to the standard system
through reliable transformations based on CCD observations of a
sufficient number of carefully selected standard stars. In the
case of the 
system the situation unfortunately is that
the primary standard stars (Crawford & Mander 1966;
Crawford & Barnes 1970; Grønbech et al.
1976; Olsen 1983; Perry et al. 1987;
Olsen 1993) are too bright for most CCD observations, and
a complete enough sample of fainter secondary standards, as
available for UBVRI photometry (Landolt 1992), has furthermore
not yet been established. Lists of candidates, often created for
a specific project, are available (see e.g. Sect. 2 (click here)), but for
various reasons they often turn out to be insufficient for other
investigations. This was the case for an ongoing project on
eclipsing binaries and population studies in the Magellanic
Clouds (MC). We have therefore decided, as an integrated part of the
project, to establish new accurate standard 
indices for
a wide grid of stars which could serve as secondary standard stars.
They were observed together with numerous
primary standards, and
our results are presented in Table 5 (click here). Selection and observation
of the candidates, transformation to the standard system, and a
comparison with published photometry is presented in the
following sections.
Table 1: Extinction coefficients
Table 2: Transformation coefficients. Mean values of scale and
colour term (b-y) coefficients are given; see Grønbech et al.
(1976) for the notation. Zero points were determined
independently for each night. K is the coefficient to 
in
the linear 
transformations. 
is the number of standard stars
observed during each period
Table 3: Catalogue of transformed uvby indices for the observed
primary standard stars. T is the uvby transformation region: A (BAF), D (GKV), G (GKIII).
N is the number of observations; the internal rms errors of one observation (m.e.)
are given. The last four colums give the differences d = standard value - transformed value in units
of 0.001 mag
Table 3: continued
Up: Secondary standard stars
