We derive fundamental parameters for the old , rich open cluster NGC 1245 using BVI photometry from the MDM 1.3m and 2.4m telescopes .
Based on detailed isochrone fitting , we find NGC 1245 has a slightly sub-solar metallicity , { [ Fe / H ] } = -0.05 \pm 0.03 ~ { } { ( statistical ) } \pm 0.08 ~ { } { ( systematic ) } , and an age of 1.04 \pm 0.02 \pm 0.09 Gyr .
In contrast to previous studies , we find no evidence for significant differential reddening .
We determine an extinction of A _ { V } = 0.68 \pm 0.02 \pm 0.09 mag and a distance modulus of ( m - M ) _ { 0 } = 12.27 \pm 0.02 \pm 0.12 mag , which corresponds to a distance of 2.8 \pm 0.2 ~ { } { Kpc } .
We derive a logarithmic mass-function slope for the cluster of \alpha = -3.12 \pm 0.27 , where a Salpeter slope is \alpha = -1.35 .
Fits to the radial surface-density profile yield a core radius of r _ { c } = 3.10 \pm 0.52 ~ { } { arcmin } ( 2.57 \pm 0.47 ~ { } { pc } ) .
NGC 1245 is highly relaxed and contains a strongly mass segregated population .
The mass function for the inner cluster has a very shallow slope , b = -0.56 \pm 0.28 .
In contrast , the outer periphery of the cluster is enriched with low mass members and devoid of high mass members out to the tidal radius , r _ { t } = 20 arcmin ( 16.5 { pc } ) .
Based on the observed surface-density profile and an extrapolated mass function , we derive a total cluster mass , M = 1300 \pm 90 \pm 170 M _ { \odot } .