CCD photometry on the intermediate-band uvbyCa H \beta system is presented for the metal-deficient open cluster , NGC 2243 .
Restricting the data to probable single members of the cluster using the CMD and the photometric indices alone generates a sample of 100 stars at the cluster turnoff .
The average E ( b - y ) = 0.039 \pm 0.003 ( s.e.m . )
or E ( B - V ) = 0.055 \pm 0.004 ( s.e.m .
) , where the errors refer to internal errors alone .
With this reddening , [ Fe/H ] is derived from both m _ { 1 } and hk , using b - y and H \beta as the temperature index .
The agreement among the four approaches is excellent , leading to a final weighted average of [ Fe/H ] = –0.57 \pm 0.03 ( s.e.m . )
for the cluster , on a scale where the Hyades has [ Fe/H ] = +0.12 .
Using a combination of photometric and spectroscopic data , 27 probable cluster members are identified and used to delineate the red giant branch and a well-defined clump at V = 13.70 , while eliminating the so-called second clump at V = 14.1 .
Interpolation between isochrones of appropriate [ Fe/H ] leads to an apparent modulus of ( m - M ) = 13.15 \pm 0.1 and an age of 3.8 \pm 0.2 Gyr .
A differential CMD comparison with Berkeley 29 , a cluster with a galactocentric distance almost twice that of NGC 2243 , constrains Berkeley 29 to be at least as young and as metal-rich as NGC 2243 .