polynomial fits to the $M_V$ vs $(B-V)_o$ relation are made for each type of star; the fitting formula and the coefficients of the fits are provided in Table 2. For G, SG, and AGB stars with abundances $\feh < -2.5$, we use the tabulated relation for $\feh=-2.5$. For D stars we employ an interpolation/extrapolation procedure among the tabulated relations. Figure 2a demonstrates the adopted $M_V$ vs $(B-V)_o$ relations of G, SG, and AGB stars at metal abundances appropriate for M92$+$M15 ($\feh=-2.20$), M13 ($-1.65$) and 47 Tuc ($-0.71$), whereas Figure 2b shows those of D stars for M92$+$M15, 47 Tuc, and Hyades. Unfortunately, there remains some additional uncertainty for TO stars, due to their positions at the “curved” part of the adopted $M_V$ vs $(B-V)_o$ relation. We employ the following approximate method. For a given $(B-V)_o$ color, $M_V$’s assuming both a D and SG classification are first estimated. If $\mvd$ is brighter than $\mvsg$, $\mvd$ is adopted as $\mvto$. If this is not the case, the intermediate $M_V$ which locates between $\mvd$ and $\mvsg$ is calibrated using the formula given in Table 2. This formula is designed to reproduce the turnoff point from neighboring points of the isochrones used in Beers 