In order to separate bright (
) cluster members from field
stars, kinematical (mainly proper motion) studies have been carried out in
all cluster regions except NGC 3228. Relative proper motions have been
determined in the regions of NGC 4103, NGC 5662 and NGC 6087 by King
(1979, 1980 and 1982 respectively) and the probability of cluster
membership for individual stars has also been derived. Other details of
the proper motion studies are given in Table 2 (click here). Using these proper
motion data, Sagar & Bhatt (1989a,b) have studied the
internal kinematics in NGC 4103, NGC 5662 and NGC 6087 and found that within
the errors of measurement intrinsic dispersions are independent of stellar
mass and radial distance.
Table 2: Details of the proper motion studies carried
out by King (1979), (1980) and (1982) for NGC 4103, NGC 5662 and NGC 6087
respectively. Relative proper motions have been determined
for 
stars. Out of them 
are liekly cluster members.
and 
are the orthogonal components of the
intrinsic proper motion dispersion determined by Sagar & Bhatt
(1989a,b)
A description of the earlier photometric and spectroscopic studies of the clusters under study is given below:
500 pc on the inner edge of the Carina-Cygnus arm of our
Galaxy. This is the nearest but least studied cluster in our sample. The
only detailed photometric study of the cluster is by Hogg (1963).
He carried out photoelectric observations of 26 stars in the UBV passbands.
Only eleven of these are photometric members. The cluster suffers with
very small interstellar extinction (see Table 1 (click here)). Hartoog
(1976) determined the spectral types for 13 stars, one of them an Am
star.
and spectral types of 12 brighter stars. These studies indicate that
all brighter cluster members are dwarfs with spectral types later than B2,
while there are no red giant members. Stetson (1981) carried out
four colour and H
photometry for 20 B-type stars in the cluster
region. This study indicates that the cluster may contain an extreme
Be star, perhaps with a circumstellar dust shell; there are also
several stars with anomalously strong H
absorption for their
temperature and luminosities. All photometric studies indicate that
interstellar extinction in front of the cluster is almost uniform,
with a value of colour excess 
.
, 
) is the 
brightest
member of the cluster sequence and has a proper motion cluster membership
probability of 84% (cf. King 1979). A detailed Strömgren
photometric and medium-dispersion spectroscopic study of the object
has been done by Bell et al. (1987).
in the UBV system. Recently, Clariá et al. (1991)
presented UBV photoelectric photometry for 237 stars brighter than 
as well as DDO and Washington photometry for three red stars.
Strömgren photometry of 27 B- and A- type stars brighter than 
is presented by Schneider (1987). This and
spectroscopic work by Fitzgerald et al. (1979) indicate that there
are chemically peculiar stars in the cluster. All the photometric studies
indicate that reddening across the cluster face is variable with a mean value
of 
. However, distance estimates to the cluster vary
from 500 to 800 pc. The study by Clariá et al. (1991) indicates
that the cluster contains two red giants and two photometric variables; it
is 
80 Myr old and has a metal abundance of
relative to the Sun. 
photometry of 18, 16 and 15 stars
brighter than 
, respectively. All these studies indicate that reddening across
the cluster is uniform with 
; distance estimates to
the cluster range from 0.7 to 0.9 kpc and the cluster seems to be
old. Recently, Luck (1994) has done an
abundance analysis of three stars in the cluster region and found that 
and 
.
, so that PMS stellar
evolutionary phases in the clusters could not be studied.