Access to Astronomical Catalogues

← Click to display the menu
I/315               UCAC3 Catalogue              (Zacharias+ 2009)

Third U.S. Naval Observatory CCD Astrograph Catalog (UCAC3) Zacharias N., Finch C., Girard T., Hambly N., Wycoff G., Zacharias M.I. , Castillo D., Corbin T., DiVittorio M., Dutta S., Gaume R., Gauss S., Germain M. , Hall D., Hartkopf W., Hsu D., Holdenried E., Makarov V. , Martines M. , Mason B., Monet D., Rafferty T., Rhodes A., Siemers T., Smith D., Tilleman T., Urban S., Wieder G., Winter L., Young A., <Astron. J. 139, 2184 (2010)> =2010AJ....139.2184Z
ADC_Keywords: Surveys ; Positional data ; Proper motions Description: UCAC3 is a compiled, all-sky star catalog covering mainly the 8 to 16 magnitude range in a single bandpass between V and R. Positional errors are about 15 to 20 mas for stars in the 10 to 14 mag range. It is supplemented by proper motions and SuperCosmos and 2MASS photometric data, as well as various flags. The proper motions of bright stars are based on about 140 catalogs, including Hipparcos and Tycho, as well as all catalogs used for the Tycho-2 proper motion construction. Proper motions of faint stars are based on a re-reduction of early epoch SPM data (-90 to -10 deg Dec) plus Schmidt plate data from the SuperCosmos project (down weighted due to systematic errors of order 100 mas). The proper motions of faint stars (R ≥ 13.5) therefore should be used with caution. The unpublished plate measure data from the AGK2, the Hamburg Zone Astrograph, the USNO Black Birch Astrograph, and the Lick Astrograph have considerably contributed to improve proper motions for stars mainly in the 10 to 14 mag range (down to the UCAC3 limit for Lick data); however, these data do not cover all sky. UCAC3 features a number of major differences with respect to UCAC2: - complete sky coverage - re-reduction of the pixel data with better modeling - double stars are resolved to the limit of the data - significantly improved photometry from CCD data - slightly deeper limiting magnitude with larger number of stars/area - reduced systematic errors of CCD observations - the addition of several new catalogs for improved proper motions - photometry in the B, R, and I bands from the SuperCosmos project - minor planet observations have been sorted out - identification of more high proper motion stars - match with 2MASS extended sources and LEDA galaxies Additional details will be published in the upcoming release paper (Zacharias et al. 2009) and in several technical papers describing details of the reduction procedures and results. For the latest updates see http://www.usno.navy.mil/usno/astrometry . Requests for the data DVD should be sent to ; technical questions can be addressed to . Acknowledging UCAC3: The release paper (Zacharias et al. 2009) should be cited whenever UCAC3 data is utilized. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file out.sam 252 103 Sample UCAC3 output ucac3doc.txt 79 1205 Description of UCAC3
See also: http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/ucac : UCAC home page I/289 : UCAC2 Catalogue (Zacharias+ 2004) I/247 : The AC2000 Catalogue (Urban+ 1997) I/259 : The Tycho-2 Catalogue (Hog+ 2000) I/277 : SPM Catalog 2.0 (Platais+ 1998) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006) VII/242 : LEDA galaxies with DENIS measurements catalog (Paturel+, 2005) VII/248 : Quasars and Active Galactic Nuclei (12th Ed.) (Veron+ 2006) Byte-by-byte Description of file (# headlines): out.sam
Bytes Format Units Label Explanations
1- 10 A10 --- 3UC UCAC3 designation (1) 12- 22 F11.7 deg RAdeg Right ascension (degrees), ICRS, Ep=J2000 23- 33 F11.7 deg DEdeg Declination (degrees), ICRS, Ep=J2000 35- 37 I3 mas e_RAdeg Minimal mean error on RAdeg (at EpRA) 39- 41 I3 mas e_DEdeg Minimal mean error on DEdeg (at EpDE) 43- 46 I4 mas ePos Error of position at Epoch=J2000 (9) 48- 54 F7.2 yr EpRA Central epoch for mean RA 56- 62 F7.2 yr EpDE Central epoch for mean Declination 64- 69 F6.3 mag f.mag ? UCAC fit model magnitude (579-642nm) (2) 71- 76 F6.3 mag a.mag ? UCAC aperture magnitude (579-642nm) (2) 78- 82 F5.3 mag e_a.mag ? Mean error on f.mag and a.mag (3) 84- 85 I2 --- ot [-2,3] UCAC object classification flag (4) 87 I1 --- db [0,7] double star flag (5) 90- 91 I2 --- Na Number of UCAC observations for the star 94- 95 I2 --- Nu Number of used UCAC observations (6) 97- 99 I3 --- Ca Number of catalog positions 102-103 I2 --- Cu Number of catalog positions used for pm's 105-112 F8.1 mas/yr pmRA ? Proper motion in RA(*cos(Dec)) 114-121 F8.1 mas/yr pmDE ? Proper motion in Dec 123-126 F4.1 mas/yr e_pmRA ? Mean error on pmRA 128-131 F4.1 mas/yr e_pmDE ? Mean error on pmDE 133-141 I09 --- MPOS [1,140051297] mean position (MPOS) number (17) -------------------------------------------------------------------------------- 143-152 I10 --- 2Mkey ? 2MASS (Cat. II/246) Unique source identifier 154-159 F6.3 mag Jmag ? J magnitude (1.2um) from 2MASS 161-164 F4.2 mag e_Jmag ? Mean error (rounded to 0.01mag) 165 A1 --- --- [:] 166-167 I02 --- q_Jmag [0,58]? J-band quality-confusion flag (7) 169-174 F6.3 mag Hmag ? H magnitude (1.6um) from 2MASS 176-179 F4.2 mag e_Hmag ? Mean error (rounded to 0.01mag) 180 A1 --- --- [:] 181-182 I02 --- q_Hmag [0,58]? H-band quality-confusion flag (7) 184-189 F6.3 mag Kmag ? K magnitude (2.2um) from 2MASS 191-194 F4.2 mag e_Kmag ? Mean error (rounded to 0.01mag) 195 A1 --- --- [:] 196-197 I02 --- q_Kmag [0,58]? K-band quality-confusion flag (7) -------------------------------------------------------------------------------- 199-200 I02 --- sc [0,14]? Supercosmos mean object + 'blend' class (10) 202-207 F6.3 mag Bmag ? B magnitude from Supercosmos 208 A1 --- --- [:] 209-210 I02 --- q_Bmag [-1,3]? B-band quality-confusion flag (11) 212-217 F6.3 mag R2mag ? R magnitude from Supercosmos 2nd epoch 218 A1 --- --- [:] 219-220 I02 --- q_R2mag [-1,3]? R-band quality-confusion flag (11) 222-227 F6.3 mag Imag ? I magnitude from Supercosmos 228 A1 --- --- [:] 229-230 I02 --- q_Imag [-1,3]? I-band quality-confusion flag (11) -------------------------------------------------------------------------------- 232-241 A10 --- catflg matching flags for 10 catalogues (12) 242 A1 --- --- [.] 243 I1 --- g [0,3]? g-flag from SPM (13) 244 I1 --- c [0,7]? c-flag from SPM (14) 246-248 I3 [6arcsec] LEDA LEDA I-band galaxy match (15) 250-252 I3 arcsec 2MX 2MASX K-band match (16)
Note (1): the 3UC number is the recommended identification of UCAC3 stars. It made as "zzz-nnnnnnn", where zzz is the zone number (between 1 and 360 from South pole to North pole), and nnnnnn a 6-digit running number in the zone. For instance, 3UC180-000007 designates the 7th star in the 180th zone (declination range between -0.5 and 0.0°) Note (2): systematic errors are expected to be below 0.1mag. The aperture photometry (a.mag) is considered more robust, particularly for "odd" cases, while the model fit magnitude is expected to be more accurate for "well behaved" stars. Note (3): computed from the scatter of individual observations on different CCD frames, and also from a S/N ratio modelisation; the larger is reported here, but was limited to 0.9mag if larger than 0.9mag. Note (4): The object type flag is used to identify possible problems with a star and has the following meaning: -2 = warning: object could be from possible streak -1 = warning: object is near overexposed star 0 = good star 1 = good star (data copied from another entry) 2 = warning: contains at least 1 overexposed image 3 = warning: all images are overexposed or "bad" Note (5): The double star flag is a double star flag used to indicate Note (5): The double star flag is a double star flag used to indicate the type/quality of double star fit with the following meaning: 0 = single star 1 = primary of pair with unreal secondary = single 2 = forced separation, on same frame 3 = blended image, some CCD frames show single star, some double 4 = forced separation, 2 objects on same frame number 5 = primary component of real double 6 = secondary component of real double 7 = other "odd" case Note (6): A zero for the number of used images indicates that all images have some "problem" (such as overexposure). In that case an unweighted mean over all available images (Na) is taken to derive the mean position, while normally a weighted mean was calculated based on the "good" images, excluding possible problem images (Nu ≤ Na). Note (7): For each 2MASS bandpass a combined flag was created (cc_flg + ph_qual) consisting of the contamination flag (0 to 50) and the photometric quality flag (0 to 8). 0 = cc_flg 2MASS 0, no artifacts or contamination 10 = cc_flg 2MASS p, source may be contaminated by a latent image 20 = cc_flg 2MASS c, photometric confusion 30 = cc_flg 2MASS d, diffraction spike confusion 40 = cc_flg 2MASS s, electronic stripe 50 = cc_flg 2MASS b, bandmerge confusion 0 = no ph_qual flag 1 = ph_qual 2MASS X, no valid brightness estimate 2 = ph_qual 2MASS U, upper limit on magnitude 3 = ph_qual 2MASS F, no reliable estimate of the photometric error 4 = ph_qual 2MASS E, goodness-of-fit quality of profile-fit poor 5 = ph_qual 2MASS A, valid measurement, snr>10 AND cmsig<0.10857 6 = ph_qual 2MASS B, valid measurement, snr> 7 AND cmsig<0.15510 7 = ph_qual 2MASS C, valid measurement, snr> 5 AND cmsig<0.21714 8 = ph_qual 2MASS D, valid measurement, no snr OR cmsig req. For example the value 05 is decoded to be cc_flg=0, and ph_qual=5, meaning no artifacts or contamination and 2MASS qual flag = "A". Note (9): taking into account the propagation of the proper motion error between the mean epoch and J2000. Note (10): "sc" is a combination of the SuperCOSMOS "meanclass" and modified "blend" flag (meanclass + blend) originally for each magnitude (B, R1, R2, I). The flag provided here is the maximum value over all bands for each of the 2 flags. The SuperCOSMOS mean class flag is an estimate of image class based on unit-weighted mean of individual classes from (B, R1, R2, I). The SuperCOSMOS modified blend flag indicates if blending is detected. The "meanclass" has the following meaning from SuperCOSMOS: 1 = galaxy 2 = star 3 = unclassifiable 4 = noise The modified "blend" flag has the following meaning: 0 = no blending 10 = possible blending detected Note (11): modified quality flag from the "qualB", "qualR2", and "qualI" quality flag from SuperCOSMOS, which gives an indication of the quality of the image from the three bands (B, R2, I). The modified quality flag has the following meaning: -1 = qual blank in SuperCOSMOS, no flag given 0 = qual zero in SuperCOSMOS, no problems detected 1 = qual < 128 in SuperCOSMOS, reliable image 2 = qual < 65535 in SuperCOSMOS, problems detected 3 = qual ≥ 65535 in SuperCOSMOS, spurious detection Note (12): The catflg provides reference to 10 major catalogs used in the computation of the proper motions and catalog matching. Each of the 10 numbers range from 0 to 6 and are the "mmf" (multiple match flag) with respect to each of the 10 following catalogs, from left to right: 1 = Hip (Hipparcos, Cat. I/239) 2 = Tycho (Tycho-2, Cat. I/259) 3 = AC2000 (Cat. I/247) 4 = AGK2-Bonn 5 = AGK2-Hamburg 6 = ZA (Hamburg Observatory Zone Astrograph) 7 = BY (USNO Black Birch Astrograph, Yellow lens) 8 = Lick (50cm Lick Astrograph) 9 = SuperCosmos (http://www-wfau.roe.ac.uk/sss) 10 = SPM (Souther Proper Motion, Cat. I/277) The value for each byte, the mmf flag, has the following meaning: 0 = star not matched with this catalog 1 = unique match, not involving a double star 2 = closest match, not involving a double, likely o.k. 3 = unique match, and involving a double star 4 = closest match, and involving a double, likely o.k. 5 = maybe o.k. smallest sep. match in both directions 6 = maybe o.k. smallest sep., but involves a double star Note (13): The g-flag from the Yale San Juan first epoch Southern Proper Motion data (YSJ1, SPM) has the following meaning: 0 = no info 1 = matched with 2MASS extended source list (2MASX, Cat. VII/233) 2 = LEDA galaxy (Cat. VII/242, http://leda.univ-lyon1.fr/) 3 = known QSO (Veron-Cetty & Veron 2006, Cat. VII/248) Note (14): The c-flag from the Yale San Juan first epoch Southern Proper Motion data (YSJ1, SPM) indicates which input catalog has been used to identify stars for pipeline processing: 1 = Hipparcos (Cat. I/239) 2 = Tycho2 (Cat. I/259) 3 = UCAC2 (Cat. I/289) 4 = 2MASS-PSC (Cat. II/246) 5 = 2MASS-XSC (extended sources, largely galaxies, Cat. VII/233) 6 = LEDA (confirmed galaxies, Paturel et al. 2005, Cat. VII/242) 7 = QSO (Veron-Cetty & Veron 2006, Cat. VII/248) Note (15): value is either 0 (no match) or contains the log of the apparent total diameter (in 0.1arcmin) for I-band (object size) information copied from the LEDA catalog (galaxies). A size value of less than 1 has been rounded up to 1. Note (16): This flag is either 0 (no match) or contains the length of the semi-major axis of the fiducial ellipse at the K-band (object size, in arcsec) information copied from the 2MASS extended source catalog. If the size is larger than 127, the flag was set to 127. Note (17): this running star number, when smaller than 140million, starts in regions near the South Pole, and increases in zones with increasing declination; not all numbers are present. Numbers over 140000000 indicate high proper stars which were identified in UCAC pixel data from matches with known high proper-motion stars.
Acknowledgements: It is a pleasure to thank Charlie Finch and Norbert Zacharias, who wrote most of this and answered to many questions. History: * 16-Aug-2009: Catalog presented with MPOS number as main UCAC3-ID * 09-Sep-2009: Added 3UC ID, recommended designation of UCAC3 stars.
(End) Francois Ochsenbein [CDS] 09-Sep-2009
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© UDS/CNRS

Contact