All Figures

	Figure 1: Absolute number of BSS in the most BSS-rich open clusters (AL07) vs. their Galactic latitude.
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In the text

Figure 2: Location in the CMD of NGC 7789 of BBS and field stars. In the upper left panel we show CMDs of NGC 7789 from Gim et al. (1998) for all stars brighter than and within the cluster radius (see Table 1). In the upper right panel, the CMD of an equal area field is shown for comparison. The cluster and field area are indicated in the lower panel, where the field of NGC 7789 covered by Gim et al. (1998) photometry is shown. In this panel the innermost circle indicates the cluster area, while the two outermost circles illustrate the field selection. This annulus have been chosen to have the same area and at the same time to be as far as possible distant from the cluster, to avoid contamination from NGC 7789 external halo stars. In all the panels filled squares (in red in the electronic version) refer to BSS stars, according to AL07 criteria (see text). Different color filled squares (in cyan in the electronic version) are used for the BSS members of NGC 7789. In the CMDs, the two solid lines are an isochrone and a ZAMS drawn for the value of the fundamental parameters of NGC 7789 (see Table 1). The dashed line (blue in the electronic version) has been drawn for the typical distance of the Perseus arm in the NGC 7789 direction.

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In the text

Figure 3: Upper panels: CMD of Berkeley 66 for cluster ( left) and field ( right) regions, as defined in the lower panel, where the innermost circle is drawn by adopting 2.0 arcmin for the cluster radius (see Table 1). The region outside the cluster area and limited by the outermost circle has the same area as the cluster region. Solid symbols (red in the electronic version) indicate BSS candidates. The solid lines are a ZAMS and an isochrone for the most accepted values of the cluster fundamental parameters (as in Table 1), whereas the dashed line (blue in the electronic version) indicates the expected location of young stars at the distance of the Perseus arm.

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In the text

Figure 4: Upper panels: CMD of Berkeley 70 for cluster ( left) and field ( right) regions, as defined in the lower panel, where the innermost circle is drawn by adopting 2.5 arcmin for the cluster radius (see Table 1). The region outside the cluster area and limited by the outermost circle has the same area of the cluster region. Solid symbols (red in the electronic version) indicate BSS candidates. The solid lines are a ZAMS and an isochrone for the most accepted values of the cluster fundamental parameters (as in Table 1).

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In the text