Binary Star Observations with the Hubble Space Telescope Fine Guidance Sensors. I. ADS 11300

According to an orbit based on measures mostly near apastron, the binary ADS 11300 = Hu 581 = WDS 18229 + 1458 passed through periastron in 1984 at an angular separation below 0.1 arcsec. On the assumption that one accurate measurement near periastron may serve to define its orbit, ADS 11300 was selected for Early Release Observation (ERO) with the Hubble Space Telescope Fine Guidance Sensors (HST-FGS). It was observed on November 1, 1990 at an angular separation of 0.066 arcsec. Revised orbital elements predict that ADS 11300 will pass through periastron in 1992 and reach a separation below 0.01 arcsec, making it a challenging target for continued HST-FGS astrometry.