Absolute Magnitude Calibration for Giants based on the Colour-Magnitude
  Diagrams of Galactic Clusters. II-Calibration with SDSS
  We present an absolute magnitude calibration for red giants with the colour
magnitude diagrams of six Galactic clusters with different metallicities i.e.
M92, M13, M3, M71, NGC 6791 and NGC 2158. The combination of the absolute
magnitudes of the red giant sequences with the corresponding metallicities
provides calibration for absolute magnitude estimation for red giants for a
given $(g-r)_{0}$ colour. The calibration is defined in the colour interval
0.45 $\leq(g-r)_{0}\leq$ 1.30 mag and it covers the metallicity interval
$-2.15\leq \lbrack Fe/H \rbrack \leq$ +0.37 dex. The absolute magnitude
residuals obtained by the application of the procedure to another set of
Galactic clusters lie in the interval $-0.28< \Delta M \leq +0.43$ mag.
However, the range of 94% of the residuals is shorter, $-0.1<\Delta M \leq+0.4$
mag. The mean and the standard deviation of (all) residuals are 0.169 and 0.140
mag, respectively. The derived relations are applicable to stars older than 2
Gyr, the age of the youngest calibrating cluster.
