Correlation of the Hipparcos and Allegheny Observatory Parallax Catalogs

No significant difference is found between the systems of the Hipparcos and Allegheny Observatory MAP parallax catalogs. The correlation of the parallaxes of 63 stars common to both programs is 0.9995 +/- 0.0001, with an average standard deviation of the difference of 0.0023 arcsec. While there is no indication of systematic difference in the two programs, our study suggests that the formal errors in one or both catalogs are somewhat underestimated. (Author)