USNO CCD Astrograph Catalog (UCAC)

Last update: 2012 Aug 2

Introduction

UCAC is an astrometric, observational program, which started in February 1998 at CTIO. All sky observations were completed at the Naval Observatory's Flagstaff Station in May 2004, and data reduction was completed in July 2009. The UCAC3 catalog was released on August 10, 2009 at the IAU General Assembly in Rio de Janero, Brazil. Bug fixes, reduction improvements, use of NPM data for proper motions and inclusion of APASS 5-band photometry lead to the final UCAC4.

News:

UCAC4: By mid 2011 a first version of the UCAC4 was produced. It was sent to a number of testers worldwide. Feedback comments were received and by the end of 2012 an improved version of UCAC4 was produced which has further been investigated. Now we have an almost final version for about 113 million stars.
UCAC4 does not use any Schmidt plate data. Proper motions of faint stars north of Dec = -20 deg are now based on NPM data. Besides 2MASS near-IR photometry (as in previous releases) UCAC4 now includes APASS 5-band photometry. The APASS data release #6 is expected to become available in May 2012 to complete the all-sky coverage. It has been decided to wait with the UCAC4 release to include APASS DR6 data. Thus the public release of UCAC4 is scheduled for June 2012.

The UCAC4 data will be sent to CDS Strasbourg at that time and a double-sided DVD with the UCAC4 release files will be sent to addresses on our distribution list (UCAC2, UCAC3 customers). In order to assist users and 3rd party software vendors to interface with UCAC4, the following files are now available:
- ucac4_data_format = text file with explanations
- z001 = binary sample data of first zone
- z001.asc = ASCII sample data (fixed format) of same data
- u4dump.f = Fortran code to dump binay zone file(s) to ASCII
- u4access.f = Fortran code for interactive data retrieval incl. index
- u4sub.f = subroutine file needed by the above
UPDATE: As of end of July 2012, UCAC4 data files have been submitted for DVD replication and successfully transferred to CDS, Strasbourg. The public release is expected very soon. Shipment of DVDs to all customers on file will likely begin in mid-August.
UCAC3 was released 2009 August 10 at the IAU General Assembly in Rio. DVDs were shipped throughout the month of September to recipients on the distribution list (see the readme_u3 file.). The data are also available from the CDS.

The observational program is complete. The last survey fields were taken successfully on 17/18 May 2004. A final all-sky plot is presented in the final monthly progress chart.

The Bright Star Supplement (BSS) to UCAC2 is now available. It contains exactly 430,000 stars from Hipparcos and Tycho-2 data to fill in the sky area missed by UCAC2 plus the all sky bright stars not in UCAC2. The files can be obtained from (new location since mid 2006) anonymous ftp ad.usno.navy.mil, /users/nz/bss/ , please start with the "readme" file, which is also available here. A plot shows the sky distribution of all BSS stars.

UCAC3 official star numbers: While the MPOS number (last column on each data record) mainly provides a means to identify known high proper motion stars, the primary star identification number should be of the form:

3UCzzz-nnnnnn

The "3UC" is constant and indicates the UCAC3 catalog. The 3 digit "zzz" number is the zone the star is in, followed by a dash and a 6 digit number which is the record number of the star on that zone. Thus the official designation of the star 42 in zone 7 would be 3UC007-000042.
UCAC2: was released at the IAU GA in Sydney. Over 1200 copies have been distributed so far.
The catalog introduction file (readme.txt) is available. It contains a detailed description of all files, formats and notes for the user.

The paper describing the UCAC2 was published in AJ, 127, 3043-3059 (May 2004) and a pre-print is also available from (astro-ph) as entry 0403060.

The UCAC2 is now available from (Vizier, Strasbourg) as entry I/289.

A color plot shows the sky coverage of UCAC2.

UCAC2 CD-ROM files access code in C/C++ is now available from (Project Pluto).
The history of other news notes has been relocated to a separate page.

Project

Pictures

September 2001: relocation from CTIO ,
October 2001: ... to NOFS , Flagstaff, AZ
Details of the astrograph and camera.
The astrograph at USNO - December 1997.
Loading the telescope for shipment to Chile.
CTIO 16-inch dome before the UCAC project.
Setup of the astrograph at CTIO
Raising the astrograph dome.
First light picture - 47 Tucanae, Jan 10, 1998!
CTIO at day.
CTIO at night.
The USNO astrograph at Cerro Tololo, Chile - some pictures.
CTIO in winter.
The 1st floor.

Publications

For papers related to UCAC3 and UCAC4 please see respective readme files.
The paper describing the UCAC2 is published in AJ, 127, 3043-3059 (May 2004) and a pre-print is also available from (astro-ph) as entry 0403060.
Astrometric surveys in support of large telescopes, Proc. SPIE Vol. 4836, p.279; Eds. J.A.Tyson, S.Wolff, 2002, Hawaii
Sky and Telescope, July 2001, p.22 and p.65
detailed UCAC1 description, AJ 120, 2131 (Oct.2000)
UCAC1 versus Tycho-2 comparison, AJ 120, 1148 (Aug.2000)
Hubble Deep Field - South link to Hipparcos
The UCAC astrometric survey (ADASS 1999, ASP Conf.Ser. 216, 427)
Data structure and software... (ADASS 1998, ASP Conf.Ser. 172, 345)
189th AAS meeting (poster paper)
feasibility study, AJ, 113, 1925 (1997)

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