In this section, we compare the present CCD photometry with all
available previous photoelectric and photographic observations. We
have found no relevant published data for NGC 3228, while in the other
three clusters the comparison is restricted to the U, B and V pass
bands. The differences () between the present data and data
obtained by others are plotted in Figs. 5 (click here), 6 (click here) and
7 (click here) for NGC 4103, NGC 5662 and NGC 6087 respectively, while the
statistical results are given in Table 10 (click here). In the table we have
also listed the results of intercomparing the various previous photoelectric
and photographic data available for each cluster.
Figures 5 (click here)-7 (click here) and Table 10 (click here) show that:
Table 10: Statistical results of the photometric comparison.
The difference () is always in the sense present minus comparison
data. The mean and standard deviation (
) are based on N stars. A few
points discrepant by more than 3.5
have been excluded from the
analysis
Figure 5: A comparison of the present UBV photometry in NGC 4103
with data given by Wesselink (1969), Becker et al. (1976) and Pedreros
(1984). The differences () are in the sense present minus
others' data, plotted against the present CCD photometry.
Photoelectric data by Wesselink (1969) and Pedreros (1984) are denoted
by open circles and triangles respectively, while photographic data by
Wesselink (1969) and Becker et al. (1976) are denoted by filled circles
and crosses respectively
Figure 6: A comparison of the present UBV photometry in NGC 5662
with data given by Moffat & Vogt (1973), Haug (1978) and Clariá
et al. (1991). Other details are the same as in Figure 5. Photoelectric
data by Moffat & Vogt (1969), Haug (1978) and Clariá et al. (1991)
are denoted by open circles, triangles and filled circles
respectively, while photographic data by Haug (1978) are denoted by
crosses
Figure 7: A comparison of the present UBV photometry in NGC 6087
with data given by Fernie (1961), Landolt (1964), Breger (1966),
Pedreros (1984) and Turner (1986). Other details are the same as in
Fig. 5. Photoelectric data by Fernie (1961) and Landolt (1964) are
denoted by triangles, while those by Breger (1966), Pedreros (1984)
and Turner (1986) are denoted by open circles. Photographic data by
Landolt (1964) and Pedreros (1984) are denoted by crosses and filled
circles respectively