Appendix 4. 2MASS Calibration Scan Working Databases and Atlas Images
4. Calibration Scan Data Processing
b. Astrometric Calibration
Table 1 - Mean Cal-PSWDB/All-Sky PSC Position Offsets
This table contains the average and standard deviation of the position differences between point sources in the calibration scan point source WDBs and All-Sky PSC for each calibration field. The mean offsets were computed using the calibration scan positions taken from the Merged Calibration Point Source WDB.
CAUTION - The astrometric bias between the calibration scan and survey measurements varies with position in each calibration field. Therefore, the mean offsets listed below are not sufficient to correct the calibration scan astrometry to the survey reference frame.
| field | avg_dra | nra | std_dra | avg_ddec | ndec| std_ddec |
| int | real | int | real | real | int | real |
90004 -0.101258 63 0.065507 0.664400 63 0.076572
90009 0.173705 5 0.084057 0.048240 5 0.098347
90013 -0.185540 409 0.072499 0.119935 409 0.093223
90021 0.159391 67 0.137101 0.318681 67 0.127800
90067 0.258913 417 0.076927 0.278719 417 0.058886
90091 -0.382015 101 0.245006 0.248329 101 0.112766
90121 0.129954 366 0.168663 0.008764 366 0.106121
90161 -0.049997 233 0.065119 0.362070 233 0.059774
90182 0.011584 265 0.052267 0.246675 265 0.089472
90191 -0.091513 159 0.067426 0.396498 159 0.083827
90217 0.358496 991 0.077347 -0.017455 991 0.054380
90234 -0.053766 231 0.077300 0.122649 231 0.086885
90247 0.262210 448 0.071773 0.334583 448 0.072649
90266 -0.126055 61 0.112297 0.268230 61 0.196511
90272 0.363510 68 0.191690 0.149718 68 0.115646
90273 0.071783 1058 0.078254 0.125364 1058 0.079275
90279 -0.020702 2881 0.042390 -0.044939 2881 0.106011
90290 0.002562 234 0.076184 0.311523 234 0.078565
90294 -0.002287 78 0.066148 -0.007477 78 0.070928
90298 0.143202 111 0.084964 0.092429 111 0.073742
90299 0.170088 114 0.110857 -0.001135 114 0.057117
90301 0.183356 116 0.098086 -0.049314 116 0.073910
90312 0.022217 1901 0.051493 -0.105921 1901 0.062260
90330 0.067273 168 0.065557 0.228793 168 0.107043
90400 0.287129 438 0.060256 0.098818 438 0.103626
90401 0.013047 1084 0.083408 0.128971 1084 0.105291
90402 -0.005727 291 0.059154 0.093966 291 0.071999
90533 -0.049960 102 0.069361 0.414000 102 0.096267
90547 -0.045941 6348 0.040474 -0.036200 6348 0.065528
90565 0.190262 167 0.079495 0.132489 167 0.067337
90808 -0.062121 3102 0.081170 0.091917 3102 0.061914
90813 -0.036692 216 0.038452 0.232550 216 0.078876
90860 0.493318 63 0.201148 0.280514 63 0.192552
90867 0.318704 116 0.096523 0.406769 116 0.100068
90868 0.080079 122 0.074288 0.327777 122 0.094194
90893 -0.166370 73 0.148928 0.386532 73 0.107094
92026 0.000380 262 0.072875 0.158689 262 0.087898
92202 -0.026871 97 0.040583 0.462359 97 0.119346
92397 0.391959 91 0.143793 0.184193 91 0.081353
92409 -0.110621 299 0.098842 0.368741 299 0.168202
Column Explanations
field - Calibration field tile number.
avg_dra, avg_dec - Average RA and Declination position offset
(PSC - Cal-PSWDB), in arcseconds, for all stars in this calibration field.
std_ra, std_dec - Standard deviation of the mean position offset,
in arcseconds.
nra, ndec - Number of stars used the average computation.
[Last Updated: 2008 February 18; by R. Cutri]
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