Figure 1: Comparison between V magnitudes derived here and
photometry of Ortolani et al. (1985)
Figure 2: Comparison between B magnitudes derived here and
photometry of Ortolani et al. (1985)
Two previous photometric studies of Palomar 13 are available in the literature: a preliminary study of the cluster published by Ciatti et al. (1965) and photographic data published by Ortolani et al. (1985). In order to check our data for any systematic variations the photometry of Ortolani et al. (1985) has been used. Figures 1 (click here) and 2 (click here) show a comparison of the V and B magnitudes in our CCD photometry with those obtained with Ortolani et al. (1985). No systematic magnitude shift in the B and V have been found. There are significant differences for the faintest stars only (the stars No. 77 and No. 61 in list of Ortolani et al. 1985).
To outline the bright parts of the CMD still better we added the RGB,
SGB and the turnoff stars from the study of Ortolani et al.
(1985) to our B, V photometry. This was done by calculating the
coefficients of a linear transformation on the basis of all common stars and
then applying this transformation to all stars in Ortolani's list that were to
be added to our photometry. The mean standard deviations of this transform are
and 
.