Speckle interferometry at the US Naval Observatory. III.

Position angles and separations resulting from 2578 speckle interferometric observations of 590 binary stars are tabulated. This is the third in a ser ies of papers presenting measures obtained using the 66 cm refractor at the US Naval Observatory in Washington, DC, and covers the period from 1995 Ju ne through 1996 December. Program stars range in separation from 0." 2 to 4 ." 3, with a limiting magnitude of V = 11. Random errors are estimated to b e 17.0 mas in separation and 0.degrees 56/rho in position angle, where rho is the separation in arcseconds. These are the first results acquired using an improved intensified CCD detector. The new detector, in concert with an intensity-filtering technique applied in software, has permitted a 1 mag i ncrease in dynamic range, to 3.5 mag, for pairs separated by about 2 ". The instrumentation and calibration are briefly described, with an emphasis on the characteristics of the new detector. The software filter used to incre ase the dynamic range is also described.