A catalog of faint reference stars in 398 fields of extragalactic radio reference frame sources

Positions of 89,422 stars in 398 fields of extragalactic reference frame sources have been determined using the Hamburg Zone Astrograph (northern hemisphere) and the US Naval Observatory Twin Astrograph, then stationed at the Black Birch Astrometric Observatory, New Zealand (southern hemisphere). Most stars are in the magnitude range 12 less than or equal to V less than or equal to 14, and the positions are accurate to approximate to 50 mas per coordinate at the epoch of observation, which ranges from the beginning of 1976 to the end of 1991. The catalog (ERLcat) is available on-line from USNO.