Detection of metal-poor stars in the direction of the north Galactic pole

A simple approach to detecting metal-poor stars is to measure a magnesium index, which depends on the Mg H band plus the three nearby Mg b lines and is derived through intermediate-band interference filters. An empirically established line of demarcation in the Mg index versus B-V diagram separates metal-poor stars from solar-abundance stars. A further separation between metal-poor dwarfs and giants depends on B-V; primarily dwarfs for B-V < 0.55, giants for B-V > 0.7, with both dwarfs and giants falling in the transition region. For the metal-poor giants the distance from the demarcation line correlates well with [Fe/H], permitting estimates of stellar abundances. Stars in two regions on the sky in the vicinity of the north Galactic pole have been observed with such a set of filters. Eighteen stars (6% of the population of 299) in the sample covering the V range 8.7 to 15.6 and 48 stars (31% of the population of 163) in a deeper probe to V = 19.9 found through this process are suspected metal-poor stars according to their Mg indices. Twenty-three are specifically deemed giants, with [[Fe/H]] less than or equal to -1.5.