The sky was divided into 22 declination zones, divided among the 20 observatories worldwide which participated in the data gathering. By the project's conclusion, positions of 4.6 million stars had been measured, many as faint as 13th magnitude. But the positions derived from the AC data are being used, in combination with modern epoch positions, to determine accurate proper motions. In creating the AC 2000, the United States Naval Observatory has completed the reduction of the AC data to a consistent system. The resulting catalog contains 4,621,836 stars covering the entire sky.
All positions are for epochs of observation.
Following these reductions, the data were placed on the ICRS through the use of the Hipparcos catalog. The magnitudes were converted to be close to that of the Tycho B data. The resulting data were then combined into the final AC 2000 catalog. Although positional accuracies contained in the AC 2000 vary from zone to zone and star to star, most are between 150 and 300 milli-arcseconds at the mean epochs of observations. The early epochs and good accuracies make the AC 2000 positions extremely valuable for determining proper motions when combined with more modern observations.