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\begin{document}

\pagestyle{empty} ~

\vspace{25mm}

\begin{center}
{\LARGE Catalogue of Stars \\[3.5mm]
measured in the Geneva Observatory \\[3.5mm]
Photometric system \\[3.5mm]
(fourth edition) \\[7.5cm]
F. Rufener \\
\vfill
1988 } \\
\vspace{10mm}
{Observatoire de Gen\`eve - CH-1290 Sauverny - Switzerland }
\end{center}

\newpage
\pagestyle{plain} \setcounter{page}{1}
~
\vfill
\begin{center}
{\LARGE Catalogue of stars \\[2.5mm]
measured in the Geneva Observatory \\[2.5mm]
Photometric System \\[2.5mm]
(fourth edition) \\[40mm]}
{\large F. Rufener \\[10mm]
Geneva Observatory, Switzerland}
\end{center}

\vspace{20mm}

{\large Summary:} A compilation of the photoelectric measurements in the Geneva
Observatory seven colour system ($U,\;B,\;V,\;B1,\;B2,\;V1,\;G$)
is presented for
29'400 stars. The catalogue, besides the coordinates and principal bibliographic
references of each star, gives the colours (normalized  magnitudes), the
colour indices $B1-B2,\; B2-V1$ and $V1-G,$ the parameters
$d,\;\Delta,\;g,\;m_2$
and the $V$ magnitude. The number of accurate measurements and the standard
deviation of their mean value are given separately for the colours and the
$V$ magnitude. An estimation procedure of the uncertainties associated with
the photometric parameters is described in the preface. The conversions to
absolute fluxes in SI units have been described by Rufener and Nicolet (1988)
in a recent paper.

\vspace{20mm}

Key words: \parbox[t]{12cm}{ Multicolour photometry - Geneva photometric
        system - \\
             $V$~magnitude scale - Geneva parameters $d,\;\Delta,\; g$ and
             $m_2$.}

\newpage


\section{Introduction}

This catalogue contains all the stars which have been measured with the
seven colour Geneva photometric system ($U,\;B,\;V,\;B1,\;B2,\;V1,\;G$).
Observations in the northern hemisphere started in 1960; they were made from
the Jungfraujoch (3577m) and Gornergrat (3100m) observatories
which both belong to the High Altitude Research Stations. Since 1964
we also observe from our station at St~Michel l'Observatoire in the
Haute-Provence Observatory (650m). Furthermore, some measurements have
been made from
the Spanish Observatories of Izania (Tenerife, 2400m) and Calar Alto
(Almeria, 2160m). After 1971, observations have been extended to the
southern hemisphere and are carried out at the ESO Observatory at
La Silla (2400m). There, in 1975, Geneva Observatory installed
a 40~cm telescope
and in 1980 the magnitude limit as well as the precision of the measurements
were improved through its replacement by a 70~cm telescope.
Between 1960 and the summer of 1987 more than 200.000 measurements in
seven colours have been gathered. Their percentages are distributed as
follows: Jungfraujoch   5.3\%, Gornergrat 5.6\%, St~Michel 8.9\%,
La Silla 79.4\%, others 0.8\%.
This shows that the majority of the measurements are done from La~Silla where
the southern as well as the northern hemisphere are now observed for all
declinations lower than $\sim$ 15\degr .

Since 1968 two photometers were used and since 1976  three
photometers are available. Particular care was given to reproducing
the system of
instrumental passbands (same filters, same photocathodes for the
photomultipliers). The use of a differential photometer (Burnet and Rufener,
1979) has increased rapidity, reliability and precision of the measurements.
Also, systematic rapid sampling as well as the application of statistical
criteria computed in real time (Bartholdi et al., 1984) ensure good control
and efficient tests of the measurements' quality. They add to the signal
measurements a signature which characterizes the observing conditions.
Permanent vigilance and systematic procedures for reduction outside
the atmosphere
and correlation to the standard guarantee a homogeneous extension of
the systems defined by the successive catalogues (Rufener 1970, 1976, 1981
and 1988).

The stars figuring in this catalogue result from the combination of various
extensive programmes undertaken mainly by the astronomers of Geneva
Observatory. Some were done by colleagues of Lausanne and Leuven
Universities.
Since all programmes are not yet completed,  observations continue.
The work for the present catalogue has involved many colleagues during
the last twenty-eight years and it would be impossible to name all the persons
who have contributed to it.
I would like to mention, however, the exceptional and long-term
cooperations with M.~Burnet, B.~Pernier, C.~Richard and J.-J.~Schwab.
All the observatory staff has helped with the construction of the
telescopes and photometers, the
observations and reductions of the measurements and finally the compilation
of the accumulated results. I should like to seize the opportunity to
thank them all for their devotion and efficient help.

\section{Passbands of the photometric system of Geneva Observatory}

These passbands are experimentally delimited by absorbent glass filters and
the function of chromatic sensitivity of the photomultipliers which all have
$Sb\,C\!s_3 (S-11)$ photocathodes. The temperature  of the filters
and photocathodes
are regulated so as to stabilize the instrumental response. Rufener and
Maeder (1971) have derived a description of the pass-bands which define the
system which is now revised and replaced by the version published by
Rufener and Nicolet (1988). They can be used directly for calculating
theoretical colours from models of stellar atmospheres.

Figure~1 shows the responses $T_i ({\lambda})$ of these passbands to an
equiphotonic flux. Table~1 summarizes some characteristics such as

\begin{eqnarray*}
\lambda_{0,i} & = & \frac{\int \,\lambda \,T_i (\lambda )\,d \lambda}
        {\int \,T_i (\lambda) d \lambda} \\[3mm]
\mu_i^2 & = & \frac{\int \,(\lambda - \lambda_{0,i})^2\,T_i \,
        (\lambda) d\lambda}
        {\int T_i\,(\lambda )\,d \lambda} \\[3mm]
\Phi_i & = & -2.5 \log \, \int \, T_i \, (\lambda) d \lambda - \Phi_B
\end{eqnarray*}

These values can only be compared after transformation to
those obtained with the responses to
an equienergetic flux which we used in our preceding editions. The principal
conversion formulae as well as the constants  for the
transformation of the colours and the $V$ magnitude of the catalogue
that are necessary to estimate each star's absolute fluxes are described
in detail by Rufener and Nicolet (1988).

\setlength{\textwidth}{13cm}

\begin{figure}[htb]
\vspace{93mm}
\caption{\protect\small Responses for the
seven colours of the Geneva photometric
system to an equiphotonic flux. The determination of these profiles are
from Rufener and Nicolet (1988).}
\end{figure}

\setlength{\textwidth}{15.7cm}

\begin{table}[htb]
\caption{\protect\small Pass-band characteristics}

\begin{center}
\begin{tabular}{|l|r|r|r|r|r|r|r|}
\hline
 & & & & & & & \\[-2.2mm]
\multicolumn{1}{|r|}{Filter} &
        \multicolumn{1}{|c|}{U} & \multicolumn{1}{|c|}{B} &
        \multicolumn{1}{|c|}{V} & \multicolumn{1}{|c|}{B1} &
        \multicolumn{1}{|c|}{B2} & \multicolumn{1}{|c|}{V1} &
        \multicolumn{1}{|c|}{G} \\[0.2cm]
\hline
 & & & & & & & \\[-2.2mm]
$\lambda_0\;$[\AA] & 3464 & 4227 & 5488 & 4015 & 4476 & 5395 & 5807 \\[0.2cm]
$\mu\;$[\AA] & 159 & 282 & 296 & 188 & 163 & 202 & 200 \\[0.2cm]
$(\mu /\lambda_0)^2 \cdot 10^3$ & 2.11 & 4.45 & 2.91 & 2.19 & 1.33 &
        1.40 & 1.19 \\[0.2cm]
$\Phi \;$ [mag] & 0.534 & 0.000 & 0.564 & 0.869 & 1.499 & 1.297 & 1.638 \\[2mm]
\hline
\end{tabular}
\end{center}

\begin{center}
\parbox{13cm}{These characteristics refer to the passband functions
corresponding to an equiphotonic flux (Rufener and Nicolet, 1988).}
\end{center}
\end{table}

\section{Some definitions}

Our weighting methods as well as the procedures for computing the deviations
around the mean values are summarized hereafter.

a) To each observation in seven colours reduced to outside the
atmosphere and correlated to our standard a weight $p$ is assigned so that
$0 \leq p \leq 4$. The actual value of this weight depends primarily on the
photometric quality of the night (stability, homogeneity of the extinction).
It is evaluated by examining the dispersion among the points in the
correlation for each colour of the night's natural system with the
corresponding colour of the standard. The number of points and thus also the
usable duration of the night are factors in the evaluation. The attribution
of this weight can be modified for each measurement individually,
taking into account particular
circumstances pertaining to the observation of a given star
(passage of cirri, particular zenith distance, incorrect measurement
of background illumination, etc.). Independently of the colour's weight but
with the same kind of considerations (good distribution of $V$-magnitude
standards
during the night, smallness of dispersion between the night's and standard
$V$-values, etc.) a weight $q$ is assigned to the $V$-magnitude such that
$0 \leq q \leq 4$.
The choice of the weights $p$ and $q$ in the scale $0$ to $4$ results from
the application of the following criteria:

\begin{description}
\item[4] for observations of exceptional quality whose correlation with
standards is remarkably well assured.
\item[3] normal weight for all the good measurements conveniently
correlated with standards.
\item[2] weight conferred as soon as the slightest doubt exists as to the
transparency or correlation with standards.
\item[1] weight conferred as soon as no certainty of good transparency and
good correlation with standards can be obtained (case of partial night for
instance).
\item[0] this weight sanctions all measurements for which an objective risk
of error exists.
\end{description}

The weighting of the $\sim$ 200.000 measurements which contribute to the
establishment of the present catalogue has been such that the following
proportions have been obtained: $p = 0$ for 6.4\%; $p = 1$ for 4.9\%;
$p = 2$ for 13.2\%; $p = 3$ for 71.2\% and $p = 4$ for 4.3\% of the
measurements. The obviously bad measurements are eliminated from our
files.

b) When, for a given star, there are n determinations of the seven
normalized magnitudes converted to the existing standard, we use the index k
in order to number the independent determinations of the j colours (j = 1,
2, \ldots 7). We thus obtain a table of normalized magnitudes $c_{kj}$ having
n lines and seven columns. To each line corresponds a weight $p_k$. The
mean colours could be

\begin{equation}
{\overline{c}_j = \frac{\sum^n_{k=1} \, p_k \, c_{kj}}
        {\sum^n_{k=1} \; p_k} }
\end{equation}

\bigskip

with obviously $\overline{c}_2 = 0$, since our normalized magnitudes
correspond to the magnitudes of the seven colours from which the magnitude of
filter~$B$ (here numbered 2) has been subtracted. In fact, to preserve the
reality of the fluxes we operate the mean on the flux estimators. We then
prefer

\begin{equation}
\overline{c}_j = -2.5\,\log
        \left( \frac{\sum^n_{k=1} \, p_k \, 10^{-0.4 c_{kj}}}
        {\sum^n_{k=1} p_k } \right)
\end{equation}

\bigskip

This alternative has real importance when the $c_{kj}$ show dispersed values
but we do it systematically. Dispersed $c_{kj}$ occur particularly for
$U$~fluxes of faint red stars. In general, the mean colour from (2) does not
differ significantly from the one computed with (1). It is evident that for
colour 2, set arbitrarily equal to 0, it is not possible to attribute
accidental errors directly. Nevertheless, the following assumption allows an
a posteriori estimation of the deviations for each colour. Let us consider
that the sum of the observational errors per line, taken with their sign, is
equal to zero. This allows us to state that the sums of normalized magnitudes
per line must be equal. Then, using

\[ C_k = \sum^7_{j=1} c_{kj} \]

and

\[ \overline{C} = \frac{\sum^n_{k=1}\,p_k\;C_k}{\sum^n_{k=1}\;p_k} \]

we can establish a new table with

\[ c^*_{kj} = c_{kj} + \frac{1}{7}\; (\overline{C} - C_k) \]

It is easy to see that we have, for the mean of the columns in this table,
$\overline{c}^*_j \equiv \overline{c}_j$.

In our opinion, the deviations $\Delta_{kj} = c^*_{kj} - \overline{c}_j$
give a better representation of the true dispersion of the measurements. They
are used to calculate the standard deviations $\sigma_j$

\[ \sigma_j = \left[ \sum^n_{k=1} \, p_k \, \Delta^2_{kj} /
        \sum^n_{k=1} \, p_k \right]^{1/2} \]

The mean standard deviation in the column $\sigma$ (SIG for colours) of the
catalogue is given by

\[ \sigma = \frac{1}{7} \, \Sigma^7_{j=1} \; \sigma_j \]

The mean $V$~magnitude and its standard deviation $\sigma_V$ (SIG for
$V$~magnitude) are computed like the mean colours.

\[ m_V = -2.5\log\,\left( \frac{\sum^n_{k=1}\,q_k\;10^{-0.4\,m_{V_k}}}
        {\sum^n_{k=1}\,q_k}\right) \]

\[ \sigma_V = \left[ \sum^n_{k=1}\,q_k\,(m_{V_k} - m_V)^2 / \sum^n_{k=1} \,q_k
        \right]^{1/2} \]

It is obvious that the values of $\sigma_j$, therefore $\sigma$ and
$\sigma_V$, do not have the statistical significance of a standard deviation
as long as the number of measurements $n$ is too small. Nevertheless for
values of $n \leq 5$, these quantities allow us to find those stars for
which one may suspect the dispersion of the first measurements to be abnormally
large. When $n > 5$, the values of $\sigma$ and $\sigma_V$ become estimations
of the true accuracy of the observations. We shall come back to this point
later.

c) We have made use of three parameters to define the mean value of
several measurements: their individual weights, $p_k$ and $q_k$, and their
total number $n$. When we have to compute a standard deviation for the mean
value of several measurements, we need a number equivalent to the number of
good measurements. We will use

\[ P = \frac{1}{3}\;\sum^n_{k=1}\;p_k \quad {\rm for\,the\,colours\,and}
\qquad \qquad Q = \frac{1}{3}\;\sum^n_{k=1}\;q_k
\quad {\rm for\,the\,}V{\rm\,magnitude} \]

These numbers, rounded off to the nearest integer, are in the columns $P$
and $Q$
of the catalogue. The above definitions explain why we sometimes obtain a
standard deviation for a star which has $P$ or $Q$ equal to 1.

\section{Calculation of a confidence interval}

Before we formulate and apply a method permitting an objective calculation
of the "error bars" for the photometric quantities resulting from the use of
the normalized magnitudes of the catalogue, we want to point out a fact
observed for the majority of the deviation tables $\Delta_{kj}$ as defined
in the preceding section. The deviations of one line are not independent and
they are very often correlated to the mean wavelength of the colour j. This
fact can be interpreted by considering that at least part of the deviation
reflects a residual error in the value of the atmospheric extinction used for
the reduction to outside the atmosphere. As a matter of fact, any error in the
assumed instantaneous extinction will strongly depend upon the wavelength.
This type of error is very frequent and affects all the stars. Another cause
which could produce similar effects would be slight changes in the star's
colour temperature. This second cause can only be invoked in the case of a
few particular stars.

We calculate the variances of the deviations for each mean colour of
subscript~i, respectively~j, as well as the covariances between them. We
thus obtain a symmetric matrix $s_{ij}$. The calculation has been made for
stars measured a great number of times. This matrix $s_{ij}$ varies from
star to star. A global matrix $S_{ij}$ has been calculated for three samples
of well measured stars having $\sigma \leq .010$ and $\sigma_V \leq .012$.
For each sample, the matrix $S_{ij}$ represents the variance and covariance
of a large table of deviations composed from the association of the
$\Delta_{kj}$ obtained with each of the sample stars. Sample~1 is composed
of stars for which the sum of the weights $p$ obtained for the third
Catalogue (Rufener, 1981) was 50 or more and for which a sum of weights $p$
superior or equal to 50 has been obtained in the meantime. Sample~2 has been
selected in the same way but by limiting to 20 the sum of weights $p$
obtained before and after the catalogue of 1981. As to sample~3 it is
composed of all stars for which we have over 50 for the sum of weights,
regardless of when they were gathered. Table~2 gives a description of
these samples with their main properties. The $S_{ij}$ matrices calculated
for each sample are similar; we retain as characteristic example the matrix
of sample~2 as it is based on a large number of measurements
of stars from both hemispheres. This matrix is given in Table~3.
The $S_{ij}$ matrix shows
the above-mentioned dependence of the deviations on the mean wavelength of
the colours. This effect is essentially caused by differential extinction
errors since stars suspected of variability have been eliminated from the
sample used. The $V$~magnitude variance and covariances prove that no
significant correlation exists between the $V$~magnitude and colour deviations.

For stars having $V$~magnitude $\leq 11.0$ we can now formulate the manner of
calculating the confidence intervals with maximum objectivity. Let $x$ be a
photometric parameter defined by a linear combination of normalized magnitudes
and calculated with values of known weight $P$,

\[ x = \sum_j \; \lambda_j \, c_j \]

The variance, and consequently the standard deviation $\sigma_x$, will be
obtained in the following manner

\[ \sigma^2_x = \frac{1}{P}\,\sum_i\,\sum_j\,\lambda_i\,\lambda_j\,S_{ij}
        = \frac{1}{P} \; \left[ \sum_j \; \lambda^2_j \; S_{jj} +
        2\sum_{i < j}\;\lambda_i \lambda_j \; S_{ij} \right] \]

For some particular cases standard deviations calculated in this manner
figure in Table~4 where they are expressed in thousandths of a magnitude.
Table~4 contains the standard deviations of the $V$~magnitude, of some typical
indices and of the main parameters used in the Geneva system as defined by
Golay (1972).

>From the diagonal terms of Table~3 we can compute the typical mean standard
deviation of colours $(\sigma)$. It can be compared to the one observed for
the colour measurements, accumulated for each star of the catalogue and given
in column~14. We obtain for this mean $\sigma$ the rounded-off value of
$\sigma = 0.005$.

For the stars weaker than $m_V$ = 11.0 Figure~2 shows the variations
of $\sigma$ and $\sigma_V$ as a function of the magnitude. One should take
this variation into account, or, better, the real values per star shown in the
catalogue. We might underline that the fast increase of $\sigma$ is due to
%       \pagebreak[2]
the fact that the majority of faint stars are also red and that
the difficulty to measure $U$ is therefore dominant for the estimation
of $\sigma$.

\begin{table}[htb]
\caption{\protect\small Characteristics for samples of well-measured stars}
\begin{center}
\begin{tabular}{|l|r|r|r|r|}
\hline
 & & & & \\[-2.2mm]
sample & \multicolumn{1}{|c|}{1} & \multicolumn{1}{|c|}{2} &
          \multicolumn{1}{|c|}{3} & \multicolumn{1}{|c|}{4} \\[2mm]
\hline
 & & & & \\[-2.2mm]
\begin{minipage}[t]{75mm}
sum of $p$ before summer '79 \\ sum of $p$ after summer '79
\end{minipage} &
\begin{minipage}[t]{17mm} \raggedleft $\geq 50$ \\ $\geq 50$ \end{minipage} &
\begin{minipage}[t]{17mm} \raggedleft $\geq 20$ \\ $\geq 20$ \end{minipage} &
\begin{minipage}[t]{17mm} \vspace{-8.2mm}
        \[ \left. \begin{array}{c} ~ \\ ~ \end{array} \right\} \geq 50 \]
\end{minipage} &
\begin{minipage}[t]{17mm} \raggedleft --- \\ $\geq 180$ \end{minipage} \\[7mm]
Total number of stars & 166 & 278 & 607 & 198 \\[2mm]
Percentage of stars with $\delta > 0$ & 44 & 42 & 29 & 4 \\[2mm]
Percentage of stars with $\delta < 0$ & 56 & 58 & 71 & 96 \\[2mm]
Mean weight $P$ per star              & 164 & 124  & 86 & 128 \\[2mm]
Colour mean sigma $(\sigma)$ & $5.2~10^{-3}$ & $5.1~10^{-3}$ & $4.9~10^{-3}$ &
                                        $3.6~10^{-3}$ \\[2mm]
$V$ magnitude mean sigma $(\sigma_V)$ & $6.1~10^{-3}$ & $6.2~10^{-3}$ & $6.2~10^
   {-3}$ &
                                        $4.4~10^{-3}$ \\[2mm]
\begin{minipage}[b]{75mm}
Estimation of the total number of measurements represented by the sample
\end{minipage}
        & $\sim$ 31.500 & $\sim$ 40.000 & $\sim$ 60.000 & $\sim$ 28.000 \\[2mm]
\begin{minipage}[b]{75mm}
Percentage of the total number of measurements represented by the sample
\end{minipage}
        & 16\% & 20\% & 30\% & 22\% \\[2mm]
\hline
\end{tabular}
\end{center}
\end{table}

\begin{table}[htb]
\caption{\protect\small Covariance matrix
        (variances and covariances are multiplied by $10^6$)}

%       \vspace{1cm}
\begin{center}
\setlength{\tabcolsep}{3mm}
\begin{tabular}{|ll||r|r|r|r|r|r|r||r|}
\hline
 & & & & & & & & & \\[-2.2mm]
~ & \multicolumn{1}{c||}{j} & \multicolumn{1}{|c|}{1} &
\multicolumn{1}{|c|}{2} & \multicolumn{1}{|c|}{3} &
\multicolumn{1}{|c|}{4} & \multicolumn{1}{|c|}{5} &
\multicolumn{1}{|c|}{6} & \multicolumn{1}{|c||}{7} &  \\[0.2cm]
& \multicolumn{1}{c||}{~} & \multicolumn{1}{c}{U} &
\multicolumn{1}{|c|}{B} &
\multicolumn{1}{|c|}{V} & \multicolumn{1}{|c|}{B1} &
\multicolumn{1}{|c|}{B2} & \multicolumn{1}{|c|}{V1} &
\multicolumn{1}{|c||}{G} & \multicolumn{1}{|c|}{m$_V$} \\[2mm]
\hline
 & & & & & & & & & \\[-2.2mm]
i & & & & & & & & & \\[0.2cm]
1 & U & 60 & 2 & -14 & 2 & -10 & -17 & -21 & 2 \\[0.2cm]
2 & B &   & 17 & -1 & 4 & -5 & -7 & -11 & -2 \\[0.2cm]
3 & V &  &  & 21 & -7 & -4 & 3 & 3 & 3 \\[0.2cm]
4 & B1 & &  &  & 21 & 0 & -7 & -12 & 0 \\[0.2cm]
5 & B2 & & & & & 20 & 0 & -1 & -1 \\[0.2cm]
6 & V1 & & & & & & 20 & 8 & -1 \\[0.2cm]
7 & G  & & & & & & & 33 & -1 \\[0.2cm]
  & m$_V$ & & & & & & & & 38 \\[0.2cm]
\hline
\end{tabular}
\end{center}
\setlength{\tabcolsep}{3mm}
\end{table}

\begin{table}[htb]
\caption{\protect\small Standard deviations of the main Geneva parameters
        (in thousandths of magnitude)}

\begin{center}
\begin{tabular}{|r||c|c|c|c|c|c|r|r|c|c|}
\hline
 & & & & & & & & & & \\[-2.2mm]
\multicolumn{1}{|c||}{P} & \multicolumn{1}{|c|}{$m_V$} &
\multicolumn{1}{|c|}{[U-B]} &
\multicolumn{1}{|c|}{[B-V]} & \multicolumn{1}{|c|}{[B1-B2]} &
\multicolumn{1}{|c|}{[B2-V1]} & \multicolumn{1}{|c|}{[V1-G]} &
\multicolumn{1}{|c|}{$d$} & \multicolumn{1}{|c|}{$\Delta$} &
\multicolumn{1}{|c|}{$g$} & \multicolumn{1}{|c|}{$m_2$} \\[2mm]
\hline
 & & & & & & & & & & \\[-2.2mm]
1 & 6.2 & 8.5 & 6.3 & 6.4 & 6.3 & 6.1 & 13.7 & 14.4 & 9.9 & 7.8 \\[0.2cm]
2 & 4.4 & 6.0 & 4.5 & 4.5 & 4.5 & 4.3 & 9.7 & 10.2 & 7.0 & 5.5 \\[0.2cm]
3 & 3.6 & 4.9 & 3.7 & 3.7 & 3.7 & 3.5 & 7.9 & 8.3 & 5.7 & 4.5 \\[0.2cm]
5 & 2.8 & 3.8 & 2.8 & 2.9 & 2.8 & 2.7 & 6.1 & 6.4 & 4.4 & 3.5 \\[0.2cm]
10 & 2.0 & 2.7 & 2.0 & 2.0 & 2.0 & 1.9 & 4.3 & 4.5 & 3.1 & 2.5 \\[0.2cm]
\hline
\end{tabular}
\end{center}

\begin{center}
\begin{tabular}{rl@{\hspace{12mm}}rl}
$d$ =  & [U-B1] - 1.430 [B1-B2] & $g$ = & [B1-B2] - 1.357 [V1-G] \\[3mm]
$\Delta$  =  & [U-B2] - 0.832\,[B2-G] & $m_2$  = & [B1-B2] - 0.457 [B2-V1]
\end{tabular}
\end{center}
\end{table}

\setlength{\textwidth}{13cm}

\begin{figure}[htb]
\vspace{98mm}
\caption{\protect\small Histogram of the catalogue's stars in function of the
magnitude $m_V$. Simultaneously, the variations of the mean $\sigma$ and
$\sigma_V$ of these stars (see section 7 for comments).}
\end{figure}

\setlength{\textwidth}{15.7cm}


\section{Comments concerning the conservation of the system}

They are of two orders, firstly the stability of the photometric system
has to be checked, secondly the evolution of the quality of the
measurements must be accounted for.

One of our aims during the extension of our photometry  to a large number of
stars is the conservation of the system's passbands. This imposes, on the one
hand, the conservation of the optical and photoelectric response curves
within the narrowest possible limits and, on the other hand, the permanence
of the correlation techniques while trying to avoid introducing any systematic
drifts. We gain safety and confidence with the following controls:

a) For stars of samples 1 and 2 we have calculated
the differences $\eta_j$
between the mean colours in "Rufener's 1981 Catalogue" and those of the
present one. We also compute the differences for both mean $V$~magnitudes.
The means of these differences $(\overline{\eta}_j)$ taken with their sign
should be equal to zero. For the two samples, we notice that these means are
always such that

\[ -0.0005 < \overline{\eta}_j < 0.0005 \]

b) We have calculated two means for the colours
of the stars in sample~2:
the first for measurements leading to the 1981 Catalogue, the second for new
measurements made since summer 1979. With the help of the matrix of variances
and covariances, we have estimated the standard deviations
$\sigma_{\varepsilon j}$
which the differences $\varepsilon_j$ of these two means would present. In order
to make this a global calculation applicable to all stars from the sample,
the number of measurements adopted for each mean has been evaluated
taking into account the selection criteria (sum of the weights
$p \geq 20$). This corresponds to at least 6.7 good measurements done before
and after the summer of 1979. For many of the means even more measurements
have been obtained. In order to consider this at least partially and to keep
the typical $\sigma_{\epsilon j}$  of each colour as a number expressed in
entire thousandths, we adopted a compromise of 8.5 measurements for each
mean of each star. As the differences $\epsilon_j$ should be equal to zero,
we considered the statistics of cases for which

\[      1) \quad \| \epsilon_j \| > \sigma_{\epsilon_j} \qquad\qquad
        2) \quad \| \epsilon_j \| > 2 \sigma_{\epsilon_j}    \]

It is found that 1) holds for 30\% and 2) for 6\% of the 1668 cases represented
by the six normalized magnitudes of 278 stars. These proportions are close to
those predicted by theory for the $\epsilon_j$, assuming a normal law and an
exact appreciation of the variances and covariances. Considering the fact
that some sample stars could present real physical drifts our results above
seem too favorable. Very probably the six $\sigma_{\epsilon_j}$ adopted here
are sometimes overestimated when the stars are measured frequently. Let us
add that the $\epsilon_j$ present no significant correlation with the right
ascension, the declination or the colour $j$ of stars in the sample.

c) The root mean square values $\overline{\sigma}_j$ of the above
differences $\epsilon_j$ calculated for all stars in samples~1 to 3 show
that firstly they do not depend on the sample and that secondly they are
comparable to or even lower than the ones obtained when testing Rufener's
1981 catalogue.

These three stability tests of the system are based on a large number of
observations (as large as 60.000 according to the sample) distributed over
all the nights. We can thus assert that our photometric system has not
changed in any undesirable manner and that it conserves the same photometric
significance throughout.

The time-dependent evolution of the matrices $S_{ij}$  shows an obvious
tendency
toward a variance decrease for the well measured star samples. For instance,
sample 4 which was based on measurements done in Chile after the summer of
1979 with the differential photometer, selects the 198 stars for which a minimum
of 60 and a mean of 128 good measurements have been carried out.
Matrix $S_{ij}$ which results from this sample is composed of 21\% of the
new measurements and displays very low variances.
It gives for colours $\sigma = .0036$ and for $V$~magnitude $\sigma_V =
.0044$. These values represent the acquisition conditions of the actual
measurements. The latter confirm estimations made by Waelkens and
Rufener (1985) and Waelkens (1985)
while analyzing measurements of variable stars
gathered during one or two years which were in good correlation with
the standard.

In conclusion we can say that the definiton of the colours was maintained
and thus a good homogeneity of the catalogue achieved. Also, the internal
precision of recent observations was improved. Therefore, the estimation
of the confidence interval shown in section 4 is either slightly
optimistic or pessimistic
depending on whether it is applied to measurements done
during the first or the last 10 years of the compilation.

\section{Variable stars}

Stars known as variables and designated in the fourth edition of the ''General
Catalogue of Variable Stars'' (GCVS, Kholopov, 1985-7), are generally
identified in our catalogue
by the letters VR in the remarks column and, whenever possible, directly by
their name or number. In the list of notes at the end of the catalogue we
give the type of variability according to the GCVS categories. The stars
detected as variables and identified by Rufener and Bartholdi (1982) are
listed as well and marked with the same indications as used in the original
article.
In general the observations of variable stars are carried out at random with
regard to their periods. As a result, the mean values of a few observations
sometimes have little sense. The same occurs for eclipsing binaries for
which we have recorded eclipses. We nevertheless give these means because
the associated standard deviations tell us about the amplitude of the
variations registered. When needed one can consult the individual measurements
which are at disposal in the Geneva photometric data base.
For stars having six or more good measurements $(P\; {\rm or} \;Q \geq 6)$
the computed
standard deviation for the colours or for the $V$~magnitude can indicate very
slight variations (microvariable star). We have attempted a preliminary
selection of such stars by using the criteria defined in Table~5. The limits of
these criteria have been set empirically.

\begin{table}[htb]
\caption{\protect\small Definition of the criteria of microvariability}

\begin{center}
\begin{tabular}{|c||c|c|c|}
\hline
         & \multicolumn{3}{|c|}{~} \\[-2.2mm]
        \multicolumn{1}{|c||}{Number of good} &
        \multicolumn{3}{|c|}{Standard deviation for the $V$ magnitude $\cdot 10^
3$}
        \\[2mm]
\cline{2-4}
         & & & \\[-2.2mm]
        \multicolumn{1}{|c||}{measures $Q$} & \multicolumn{1}{|c|}{\makebox[27mm
]{a}} &
        \multicolumn{1}{|c|}{\makebox[27mm]{b}}  &
        \multicolumn{1}{|c|}{\makebox[27mm]{c}} \\[2mm]
\hline
\hline
 & & & \\[-2.2mm]
2 & & & $\geq$ 40 \\[0.2cm]
3 & & & $\geq$ 25 \\[0.2cm]
4 to 5 & & & $\geq$ 20 \\[0.2cm]
6 to 10 & $\geq$ 23 & $\geq$ 18 & \\[0.2cm]
11 to 20 & $\geq$ 18 & $\geq 14$ &  \\[0.2cm]
$\geq$ 20 & $\geq$ 14 & & \\[0.2cm]
\hline
\end{tabular}
\end{center}
\end{table}

They were used with the 1981 catalogue
and have allowed 333 identifications of suspected variables (Rufener and
Bartholdi, 1982). A first application of the same criteria to the present
edition of the catalogue leads to the following inventory: some 200 stars
apply to criterion a, either variable or microvariable; about 100 satisfy
criterion b and are possible microvariables; finally, about 300 stars are
candidates for criterion c, they are suspected variables. Each case will need
another close investigation as well as complementary observations.

\section{Statistics and identification problems}

The statistics which follow will give a general view on the
acquisition, the contents and the
quality of the material gathered for this catalogue. The acquisition of
observations has developed quasi exponentially
between 1960 and 1980, with a mean annual rate of increase around 20\%. Since
1980 the situation has stabilized with an annual average close to 16.000
measurements. Each year the catalogue increases by roughly 1700 entries.
The aim is to obtain three measurements per star correlated to
a sufficient number
of standard star observations. Many observations are devoted to short
or long-term monitoring of variable stars of various types.

The distribution of the catalogue stars over the celestial sphere
is not uniform. We count between 1000 to 1200 stars per right ascension
hour, their frequency is 1.5 times larger between 5 and 9 hours.
Due to the increasing preponderance of the chilean observations, 63\% of the
stars are in the southern hemisphere while 37\% have positive declinations.
Strong concentrations of stars can be observed
around the galactic plain. Half of them are located between $\pm\,15$\degr and
one third between $\pm\,6$\degr of galactic latitude.
Cross-comparison with the Bright
Star Catalogue reveals that 83\% of its stars are now represented in
our catalogue; the missing bright stars are mostly located in the
northern sky.  Also, approximately 10\% of the HD catalogue are represented.
The $V$~magnitudes of stars in our catalogue are distributed rather evenly
around a median value close to $m_V=8.50$~. Figure~2 illustrates this
distribution. The frequency of known spectral types among the stars in our
catalogue appears as follows:

\setlength{\tabcolsep}{0.8cm}
\begin{center}
\noindent\begin{tabular}{p{30mm}rrr}
O-B   \hfill 25\% & & & \\
A-F   \hfill 30\% & A $\simeq$ 20\% & F $\simeq$ 10\% & \\
G-K-M \hfill 35\% & G $\simeq$ 15\% & K $\simeq$ 15\% & M $\simeq$ 5\% \\
\multicolumn{4}{l}{Without or other types 10\%.}
\end{tabular}
\end{center}
\setlength{\tabcolsep}{0.25cm}

We have established statistics from the standard deviations observed for the
colours $(\sigma)$ and the $V$~magnitude $(\sigma_V)$. Fig. 2 shows the
evolution, as a function of $V$~magnitude, of the mean $\sigma$ computed for
stars with $P \geq 3$. A minimum can be observed for the most
easily measurable stars. The growth of the mean $\sigma$ from the $10^{th}$
magnitude onwards is correlated with the relative increase of photon
noise. This is due to a particular circumstance. Such a rapid
increase is essentially explained by the fact that the majority of
faint stars are red and that their $U$ flux is consequently extremely weak. The
standard deviation $\sigma$ defined in section~3 increases sharply in that
case. For these stars the determination of the colours is less doubtful,
except for $U$, whose
colour is even more uncertain than indicated by $\sigma$ which is an
average over all colours.
A higher dispersion is also visible for the brightest stars whose measurement
presents certain difficulties (use of light-attenuators, possible saturation eff
   ects,
higher dispersion of the air masses due to measuring conditions). Fig.~2
also shows the evolution, as a function of $V$~magnitude, of the mean $\sigma_V$
for stars with $Q \geq 3$. An increasing effect of photon noise from
$m_V = 10$ onwards is also apparent. In both cases the estimates of $\sigma$
and $\sigma_V$ obtained in section 4 with the matrix of Table~3 are
representative for all magnitudes $m_V < 11$. We have checked that $\sigma$
and $\sigma_V$ present mean values which are almost independent of the $P$ or
$Q$ values as soon as these reach or exceed 6. This observation supports the
statement made in section~3 and justifies the limits chosen for the criteria
of microvariability in Table~5. The examination of the mean $\sigma$ computed
for each spectral type confirms a known and already published fact: $O$ and $B$
stars are frequently microvariable and $M$~stars are often variable (Maeder and
Rufener, 1972; Maeder, 1979).

We had to overcome some difficulties during the identification on sky
atlases of stars selected from the
NLTT (Luyten, 1979, 1980). Perhaps an undefined number of the proposed
measurements might not concern the star with large proper motion we had
searched for, but a neighbouring star. The probability of an identification
error is, of course, higher for weak stars. The critical discussion of
each case could not, at the present, be undertaken with all the security desired
   .
The elimination of these errors will be a long process for which we ask for
your cooperation by notifying us of any identification error you might
notice.

\section{Description of the catalogue}

\dcol{Columns 1 and 2}{The Bayer or Flamsteed designations when these exist. The
                variable star designation is given secondary priority. }
                \\[3.3mm]
\dcol{Column 3}{The number in Hoffleit's 1977 ''Catalogue of Bright Stars''
                (BS). } \\[3.3mm]
\dcol{Column 4}{The number in the ''Henry Draper Catalogue'' (HD). For
                components of multiple stars we added the suffix A, B, C...
                Usually when we know that two or more components are
                measured together a remark is made, D for optically double
                and B for spectroscopic binaries, in column 31. } \\[3.3mm]
\dcol{Column 5}{The number in the ''Durchmusterung'' (DM) according to the HD
                practice. For multiple stars we added
                the suffix A, B, C\ldots } \\[3.3mm]
\dcol{Columns 6 and 7}{Right ascension for the year 1900. } \\[2mm]
\dcol{Columns 8 and 9}{Declination for the year 1900. } \\[2mm]
\dcol{Column 10}{Galactic longitude $(\ell^{II})$. } \\[2mm]
\dcol{Column 11}{Galactic latitude $(b^{II})$. } \\[2mm]
\dcol{Column 12}{In this column we display explicitly the star's
                membership to a cluster or a group as well as the
                identification number defined in certain publications for
                which we give bibliographic references in Table 6. } \\[3.3mm]
\dcol{Column 13}{Weight $P$ of the colours defined in section 3c. } \\[2mm]
\dcol{Column 14}{Mean standard deviation $\sigma$ obtained for the colours
                as described in section 3b, in 0.001 of mag. } \\[3.3mm]
\dcol{Columns 15 to 20}{The normalized magnitudes or colours which correspond to
                our seven passbands. A normalized
                magnitude is a colour index formed in a particular manner.
                The first term is the magnitude of the colour
                considered and the second term  is always the magnitude in
                colour $B$. The description of the reduction of observations to
                outside the atmosphere and the calculation of the normalized
                magnitudes is given by Rufener (1964, 1984). } \\[3.3mm]
\dcol{Columns 21 to 23}{Colour indices selected according to their frequency
                of use. } \\[2mm]
\dcol{Columns 24 to 27}{Photometric parameters defined as follows:
\begin{center}
\begin{tabular}{r@{~~=~~}l}
                $d$      & $ [U-B1] - 1.430\,[B1 - B2]$ \\
                $\Delta$ & $ [U-B2] - 0.832\,[B2-G]$ \\
                $g$      & $ [B1-B2] - 1.357\,[V1-G]$ \\
                $m_2$    & $ [B1-B2] - 0.457\,[B2-V1]$
\end{tabular}
\end{center} } \\[2mm]
\dcol{Column 28}{Weight $Q$ of the $V$~magnitude as defined
                in section 3c. } \\[2mm]
\dcol{Column 29}{Standard deviation $\sigma_V$ obtained for $V$~magnitude
                as described in section 3b, in 0.001 of mag. } \\[3.3mm]
\dcol{Column 30}{$m_V$~magnitude of the star derived from our measurements
                alone. This $m_V$ scale is very close to that of
                the $UBV$ system (see Rufener and Maeder, 1973). } \\[3.3mm]
\dcol{Column 31}{Remarks according to the following code: \\
                D: Optical double star not separated during the measurement
                (information from various sources); \\
                B: Spectroscopic binary (information from various
                sources); \\
                V: Variable compiled in the "General Catalogue of Variable
                Stars" (GCVS) by Kukarkin et al. (1969-71) and Kholopov
                et al. (1985-7).
                Listed under the same remark are the
                microvariable stars selected by
                Rufener and Bartholdi (1982). \\
                R: Reference to a note at the end of the catalogue. These
                notes are ordered in the same manner as the catalogue, by
                increasing right ascension. The stars are identified by one
                of their numbers or by their membership to a cluster or
                group. In the absence of this information a contracted
                form of the
                equatorial coordinates gives the stars' identification. }
                \\[3.3mm]
\dcol{Column 32}{The MK spectral type when it figures in the BS, in Jaschek's
                (1964), Kennedy's (1974) or Buscombe's (1977) catalogue.
                In brackets we give the Harvard spectral type, in particular
                the one from the HD or from some other source. } \\[10mm]


{\noindent\hspace{12mm}\large Table 6 :~~Coded bibliographic references}

\vspace{5mm}

\noindent
\bref{\bf Membership}{\bf Bibliographic reference} \\[2mm]
\bref{ALF PER}{{\em Heckmann et al.}~~1956 } \\
\bref{BPM}{{\em Luyten}~~1963 } \\
\bref{BR HOR}{{\em Philip}~~1967 } \\
\bref{CHI PER}{{\em Oosterhoff}~~1937 } \\
\bref{COMA TR}{{\em Trumpler}~~1938 } \\
\bref{COMA TA}{{\em Trumpler, appendix A}~~1938 } \\
\bref{COMA AR}{{\em Argue}~~1963  } \\
\bref{COMA G}{{\em Internal numbering} } \\
\bref{CYG II}{{\em Schulte}~~1958  } \\
\bref{G}{{\em The Giclas numbered stars}~~1971 } \\
\bref{GLIESE}{{\em Gliese}~~1969  } \\
\bref{GLO NGC}{{\em Globular cluster with NGC number} } \\
\bref{HYADES B}{{\em van Bueren}~~1952 } \\
\bref{HYADES A}{{\em van Altena}~~1966  } \\
\bref{HYADES J}{{\em Johnson et al.}~~1962  } \\
\bref{H PER}{{\em Oosterhoff}~~1937  } \\
\bref{IC 348}{{\em Gingrich}~~1922  } \\
\bref{IC 1805}{{\em Vasilevskis}~~1965  } \\
\bref{IC 2082}{{\em Grenon} (to be published)  } \\
\bref{IC 2391}{{\em Perry and Hill}~~1969  } \\
\bref{IC 2602}{{\em Braes}~~1962  } \\
\bref{IC 2714}{{\em Becker et al.}~~1976  } \\
\bref{IC 4651}{{\em Lindoff}~~1972b  } \\
\bref{IC 4665}{{\em Kopff}~~1943 } \\
\bref{IC 4756}{{\em Kopff}~~1943  } \\
\bref{IC 4996}{{\em van Schewick}~~1967  } \\
\bref{LDS}{{\em Luyten's double stars}~~1972  } \\
\bref{LMC HV}{{\em Leawitt}~~1908  } \\
\bref{LS}{{\em Luminous stars in North. Milky Way (Hamburg)} } \\
\bref{LSS}{{\em Stephenson and Sanduleak}~~1971  } \\
\bref{LTT}{{\em Luyten}~~1957, 1961, 1962  } \\
\bref{MCORM}{{\em Vyssotsky and Williams}~~1948  } \\
\bref{MUR}{{\em Murray et al.}~~1987  } \\
\bref{NLTT}{{\em Luyten}~~1979, 1980  } \\
\bref{NPL}{{\em Perek and Kohoutek}~~1967  } \\
\bref{O-STARS}{{\em Hiltner and Johnson}~~1956  } \\
\bref{ORION CL}{{\em Brun}~~1935  } \\
\bref{OS}{{\em Objective Prism Survey, Stock et al.}~~1971  } \\
\bref{PHL}{{\em Haro and Luyten}~~1962  } \\
\bref{PLEI H}{{\em Hertzsprung}~~1947  } \\
\bref{PLEI T}{{\em Trumpler}~~1921  } \\
\bref{PRAE KW}{{\em Klein-Wassink}~~1927} \\
\bref{PRAE VL}{{\em Vanderlinden}~~1933  } \\
\bref{ROBERTSON}{{\em Robertson}~~1978  } \\
\bref{SA 140}{{\em Brueck}~~1935  } \\
\bref{SA 141}{{\em Brueck}~~1935 } \\
\bref{SGP A ST}{{\em Philip and Sanduleak}~~1968  } \\
\bref{SMC AZZO}{{\em Azzopardi and Vigneau}~~1975  } \\
\bref{SP 025-02}{{\em Reichen} } \\
\bref{SP 206-02}{{\em Rabattu} } \\
\bref{SP 203+02}{{\em Rabattu} } \\
\bref{SP LLL $\pm$ BB}{{\em Golay} } \\
\bref{VYSSOTSKY}{{\em Faint stars classed by Vyssotsky}~~1943-1958 } \\
\bref{WD-STARS A}{{\em Luyten}~~1949  } \\
\bref{WD-STARS C}{{\em Feige}~~1959  } \\
\bref{WD-STARS D}{{\em Giclas et al.}~~1965, 1967, 1970  } \\
\bref{WR CAT MR}{{\em Smith}~~1968  } \\
\bref{NGC 104}{{\em Grenon} (to be published) } \\
\bref{NGC 129}{{\em Arp et al.}~~1959  } \\
\bref{NGC 457}{{\em de Vegt}~~1966  } \\
\bref{NGC 581}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 654}{{\em M\"uller}~~1955  } \\
\bref{NGC 663}{{\em Wallenquist}~~1929  } \\
\bref{NGC 752}{{\em Ebbighausen}~~1939a;~~number $>$ 320: \\
{\em Mermilliod}~~(to be published)} \\[1mm]
\bref{NGC 1039}{{\em Bruggeman}~~1935  } \\
\bref{NGC 1291}{{\em Grenon} (to be published)  } \\
\bref{NGC 1313}{{\em Grenon} (to be published)  } \\
\bref{NGC 1326}{{\em Grenon} (to be published)  } \\
\bref{NGC 1502}{{\em de Vegt}~~1966  } \\
\bref{NGC 1543}{{\em Grenon} (to be published)  } \\
\bref{NGC 1545}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 1647}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 1662}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 1664}{{\em Larsson-Leander}~~1957  } \\
\bref{NGC 1778}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 1912}{{\em Cuffey}~~1938  } \\
\bref{NGC 1960}{{\em Boden}~~1951  } \\
\bref{NGC 2168}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 2169}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 2217}{{\em Grenon} (to be published)  } \\
\bref{NGC 2232}{{\em Claria}~~1972  } \\
\bref{NGC 2244}{{\em Johnson}~~1962  } \\
\bref{NGC 2251}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 2264}{{\em Walker}~~1956  } \\
\bref{NGC 2281}{{\em Vasilevskis and Balz}~~1969  } \\
\bref{NGC 2287}{{\em Cox}~~1954  } \\
\bref{NGC 2301}{{\em Grubissich and Purgathofer}~~1962  } \\
\bref{NGC 2360}{{\em Becker et al.}~~1976  } \\
\bref{NGC 2362}{{\em Johnson}~~1950  } \\
\bref{NGC 2422}{{\em van Schewick}~~1966  } \\
\bref{NGC 2423}{{\em Hassan}~~1976  } \\
\bref{NGC 2447}{{\em Becker et al.}~~1976  } \\
\bref{NGC 2451}{{\em Williams}~~1967  } \\
\bref{NGC 2516}{{\em Cox}~~1955  } \\
\bref{NGC 2539}{{\em Pesch}~~1961  } \\
\bref{NGC 2547}{{\em Fernie}~~1959  } \\
\bref{NGC 2548}{{\em Ebbinghausen}~~1939b } \\
\bref{NGC 2658}{{\em Grenon} (to be published) } \\
\bref{NGC 2682}{{\em Fagerholm}~~1906  } \\
\bref{NGC 3109}{{\em Grenon} (to be published)  } \\
\bref{NGC 3114}{{\em Jankowitz and Mac Cosh}~~1963  } \\
\bref{NGC 3293}{{\em Turner et al.}~~1980  } \\
\bref{NGC 3532}{{\em Koelbloed}~~1959a  } \\
\bref{NGC 3680}{{\em Eggen}~~1969  } \\
\bref{NGC 4755}{{\em Arp and van Sant}~~1958  } \\
\bref{NGC 5101}{{\em Grenon} (to be published)  } \\
\bref{NGC 5102}{{\em Grenon} (to be published)  } \\
\bref{NGC 5139}{{\em Grenon} (to be published)  } \\
\bref{NGC 5236}{{\em Grenon} (to be published)  } \\
\bref{NGC 5460}{{\em Claria}~~1971  } \\
\bref{NGC 5466}{{\em Cuffey}~~1961  } \\
\bref{NGC 5822}{{\em Bozkurt}~~1974  } \\
\bref{NGC 6025}{{\em Feinstein}~~1971  } \\
\bref{NGC 6067}{{\em Mermilliod numbering} } \\
\bref{NGC 6121}{{\em Alcaino}~~1975  } \\
\bref{NGC 6205}{{\em Grenon} (to be published)  } \\
\bref{NGC 6231}{{\em Seggewiss}~~1968  } \\
\bref{NGC 6254}{{\em Arp}~~1955, first digit is Roman  } \\
\bref{NGC 6281}{{\em Feinstein and Forte}~~1974  } \\
\bref{NGC 6341}{{\em Grenon} (to be published)  } \\
\bref{NGC 6397}{{\em Woolley et al.}~~1961  } \\
\bref{NGC 6405}{{\em Rohlfs et al.}~~1959  } \\
\bref{NGC 6475}{{\em Koelbloed}~~1959b  } \\
\bref{NGC 6494}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 6611}{{\em Walker}~~1961  } \\
\bref{NGC 6633}{{\em Kopff}~~1943  } \\
\bref{NGC 6752}{{\em Alcaino}~~1972  } \\
\bref{NGC 6791}{{\em Grenon} (to be published)  } \\
\bref{NGC 6811}{{\em Lindoff}~~1972a  } \\
\bref{NGC 6871}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 6910}{{\em Tifft}~~1958  } \\
\bref{NGC 6913}{{\em Tifft}~~1958  } \\
\bref{NGC 6940}{{\em Vasilevskis and Rach}~~1957  } \\
\bref{NGC 7092}{{\em Weaver}~~1953  } \\
\bref{NGC 7128 *)}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 7160}{{\em Hoag et al.}~~1961  } \\
\bref{NGC 7209}{{\em M\"avers}~~1940  } \\
\bref{NGC 7243}{{\em Lengauer}~~1937  } \\
\bref{NGC 7789}{{\em Kuestner}~~1923  } \\
\bref{NGC 7822}{{\em Mac Connel}~~1968  } \\

{\small *) This reference contains two lists of stars for each cluster. We have
used the numbers given by authors for designating stars belonging to the
first list (i.e. stars measured photoelectrically). We have then numbered
successively, and without exception, all stars belonging to the second list
(i.e. stars measured photographically). This extension of the numbering has
at times given a second number to stars figuring on both lists.}

\vspace{15mm}

A version of this catalogue exists on magnetic tape and can be obtained
from the Centre de Donn\'ees Stellaires in Strasbourg (for more details,
please consult the ``Bulletin d'Information'' of the Centre de Donn\'ees
Stellaires).

This work done in collaboration with many colleagues at Geneva Observatory
was supported by the Swiss National Foundation for Scientific Research.


\newpage

\setlength{\itemsep}{0mm}
\setlength{\parsep}{0mm}

{\noindent\large References}
\bigskip

\begin{description}
\item[]{Alcaino, G.: 1972, Astron. Astrophys. {\bf 16}, 221}

\item[]{Alcaino, G.: 1975, Astron. Astrophys. Suppl. {\bf 21}, 5}

\item[]{Argue, A.N.: 1963, Mon. Not. Roy. Astron. Soc. {\bf 127}, 97}

\item[]{Arp, H.C.: 1955, Astron. J. {\bf 60}, 317}

\item[]{Arp, H.C., van Sant, C.T.: 1958, Astron. J. {\bf 63}, 341}

\item[]{Arp, H.C. et al.: 1959, Astrophys. J. {\bf 130}, 80}

\item[]{Azzopardi, M., Vigneau, J.: 1975, Astron. Astrophys. Suppl.
        {\bf 22}, 285}

\item[]{Bartholdi, P., Burnet, M., Rufener, F.: 1984, Astron. Astrophys.
        {\bf 134}, 290}

\item[]{Becker, W., Svolopoulos, S.N., Fang, C.: 1976, Katalog
        photographischer und photoelektrischer Helligkeiten von
        25 galaktischen Sternhaufen im $RGU$- und $U_eBV$-~System
        (Obs. Basel)}

\item[]{Bidelman, W.P.: 1956, Publ. Astr. Soc. Pacific {\bf 68}, 318}

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\end{description}

\end{document}

