Electronographic Photometry of Star Clusters in the Magellanic Clouds. II. The Color-Magnitude Diagram of NGC 2209

Electronographic magnitudes and colors of stars in the cluster NGC 2209 in the Large Magellanic Cloud have been measured on electrographs taken with a Spectracon image converter attached to the f/7.S focus of the 60-inch reflector at Cerro Tololo. The color-magnitude diagram has been derived to V = 21.9 and consists of the upper end of an evolved main sequence and a yellow-giant branch, separated from the main sequence by a very small Hertzsprung gap. The cluster appears to be about as old as the Hyades, but the giant branch extends to much smaller color indices than it does in the metal-rich "Population I" open clusters in our Galaxy. Presumably, this structure results from a difference between the chemical composition of the stars in NGC 2209 and that of the stars in clusters of comparable age in our Galaxy.