第三个US海军天文台CCD星表（UCAC3）
The Third US Naval Observatory CCD Astrograph Catalog (UCAC3)
摘要：
第三个美国海军天文台（USNO）CCD星表，UCAC 3在2009年8月10日的IAU大会上发布。这是该系列中的第一个全天空版本，包含超过1亿个天体，其中约9500万个有自行，覆盖约R = 8至16等。目前的历元位置是从20厘米孔径USNO Astrograph的“红色镜头”的观测中获得的，配备了4k × 4k CCD。自行是通过将这些观测结果与超过140个地面和空间星表（包括依巴谷/第谷和AC 2000.2）以及来自其他天体照相机的5000多个未发表的测量结果相结合而得出的。对于大多数南半球的暗星，SPM程序（YSJ 1）中的耶鲁/圣胡安第一历元板块构成了自行的基础。这些数据由从超级宇宙项目获得的全天施密特板巡天天体测量和光度测定以及2 MASS近红外光度测定补充。与UCAC 2相比，UCAC 3数据的主要区别包括：全新的原始数据简化，改进了对位置系统误差的控制，光度测量显著改进，极限星等略深，覆盖北极区域，通过包括双星和弱探测而更完整。这当然会导致一个目录，这是不“干净”的UCAC 2和问题领域概述了用户在本文中。UCAC 3中恒星的位置精度约为15至100质量/坐标，视星等而定，而自行误差范围为1至10质量/年，视星等和观测历史而定，由于重新减少SPM数据和纳入更多UCAC 2时不可用的天体照相板数据，UCAC 2取得了显着改善。
英文摘要：
The third US Naval Observatory (USNO) CCD Astrograph Catalog, UCAC3 was released at the IAU General Assembly on 2009 August 10. It is the first all-sky release in this series and contains just over 100 million objects, about 95 million of them with proper motions, covering about R = 8 to 16 magnitudes. Current epoch positions are obtained from the observations with the 20 cm aperture USNO Astrograph's "red lens", equipped with a 4k by 4k CCD. Proper motions are derived by combining these observations with over 140 ground- and space-based catalogs, including Hipparcos/Tycho and the AC2000.2, as well as unpublished measures of over 5000 plates from other astrographs. For most of the faint stars in the Southern Hemisphere the Yale/San Juan first epoch plates from the SPM program (YSJ1) form the basis for proper motions. These data are supplemented by all-sky Schmidt plate survey astrometry and photometry obtained from the SuperCOSMOS project, as well as 2MASS near-IR photometry. Major differences of UCAC3 data as compared to UCAC2 include a completely new raw data reduction with improved control over systematic errors in positions, significantly improved photometry, slightly deeper limiting magnitude, coverage of the north pole region, greater completeness by inclusion of double stars and weak detections. This of course leads to a catalog which is not as "clean" as UCAC2 and problem areas are outlined for the user in this paper. The positional accuracy of stars in UCAC3 is about 15 to 100 mas per coordinate, depending on magnitude, while the errors in proper motions range from 1 to 10 mas/yr depending on magnitude and observing history, with a significant improvement over UCAC2 achieved due to the re-reduced SPM data and inclusion of more astrograph plate data unavailable at the time of UCAC2.
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