Table 3: [Fe/H] and HB morphologies from Harris (1996); r is the number ratio $r=\frac{\char93 \rm CN-strong}{\char93 \rm CN-weak}$ . References: 1 - Briley & Smith (1993); 2 - Smith & Fullbright (1997), 3 - Norris (1987), 4 - Smith (2002b), 5 - Smith & Norris (1982); 6 - Langer et al. (1992), 7 - Norris & Freeman (1983), 8 - Norris et al. (1981); 9 - Smith & Bell (1986), 10 - Smith & Mateo (1990).
Cluster
[Fe/H] HB r Sources

M 10
-1.52 0.98 0.71 1,2

M 13 -1.54 0.97 3.2 3

M 3 -1.57 0.08 0.42 4

NGC 3201 -1.58 0.08 1.00 5

NGC 1904 -1.57 0.89 2.60 6

M 22 -1.64 0.91 0.42 7

NGC 6752 -1.56 1.00 0.95 8

NGC 6934 -1.54 0.25 0.58 9

M 2 -1.62 0.96 3.5 10

NGC 7006 -1.63 -0.28 (2-3.5) this work