Hi, Magnitude of UCAC3 are better than GSC, and better than UCAC2, but far than perfect. The main goal for UCAC3 is astrometry.
Considering just the extract for Skychart, not the full dataset: - 7 time more objects - much more precise position - inclusion of proper motion to conserve precision over time - color indication - very good completeness, almost no missing star - almost no fake star, GSC include a lot of scratch, ghost, ... - much less duplicate, in GSC almost all stars in plate border appear two to four time. - many more faint stars near the bright object halo Patrick
