The CMDs for Be 64 are shown in Fig. 5 (click here). Two nearby fields towards
east and west directions away from the cluster region have also
been observed to estimate contamination of field stars in the cluster region.
The CMDs for field regions are shown in Fig. 6 (click here). A clump of red giants
appears near V = 16.4,
,
,
. A
comparison of the (V, V-R) and (V, V-I) CMDs of the cluster region and
nearby fields indicates that in the range of V= 16-17, (V-R)= 1.0-1.2 and
(V-I)= 2.0-2.3, there are 7 stars in the cluster region, whereas, in the nearby
fields there are 2 and 3 stars respectively. Since the CMDs of nearby fields
covers an area which is double as compared to the cluster region, it is
expected that at the most 2 field stars can contaminate the sample of the red
giant clump. It is rather difficult to identify the MS in the CMDs, however, a
well defined blue envelope of the MS can be easily identified in (V, V-I) and
(V, V-R) CMDs. A comparison of the (V, V-I) CMD of the cluster with the
CMDs of nearby fields manifests that cluster region has large number of stars
having
. whereas there are very few stars in the CMD of
nearby field regions having
. We have plotted a box using
thick dashed line in the CMDs of nearby fields to indicate the main distribution
of stars in the CMD. The same box is also plotted in the (V, V-I) CMD of the
cluster region. The stars in the cluster region lying in the box mainly belong to
the foreground field population. The MS of the cluster region is negligibly
affected by the field stars. Since the cluster is located at
, it
indicates that the cluster may be located outside the galactic disk.
It is impossible to estimate the BTO and BRGB using (V, B-V) CMD only,
however, we have compared the morphology of the (V, B-V), (V, V-I), (V,
V-R) CMDs and estimated V magnitude at the turnoff point on the (V, V-I)
and (V, V-R) CMDs. Then (B-V) colour corresponding to the so determined V
magnitudes was read from the (V, B-V) CMD. The (B-V) colour thus determined
was taken as BTO. The BTO colour comes out to be . The position
of BRGB is estimated at
and
. The CIP
comes out to be
which indicates an age of
.
The CMDs for Be 69 are shown in Fig. 7 (click here). CMDs for two nearby fields
towards north and south directions away from the cluster
region have also been observed to estimate contamination of field stars in the
cluster region. The CMDs for field regions are shown in
Fig. 8 (click here). The area
of the cluster region is
of the field region. Although the
contamination due to field stars is significant, still the main properties of the
cluster population can be seen in the CMD of the cluster region. The broadness of
the main sequence is due to various causes, among which are the photometric
errors, the presence of unresolved binary stars, a possible internal reddening
and field stars contamination. The BTO is estimated at
,
, and position of BRGB is estimated at
,
. The colour index parameter comes out to 0.55, which indicates
an age of
for the cluster.
Here we would like to point out that the ages obtained by using this
method are approximate. Error in eye estimate of CIP is approximately of the
order of . For a value of
, age estimate can vary
from log t= 8.7 to
.