ATCA calibrator catalogue update
Generally the positional changes have been less than 0.5 arcsec. However there is a cluster of poor calibrator positions near RA=23 hours, DEC=-40o. The accuracy and the reference for a calibrator's position is now given on the web page for each calibrator.
The consequences
The changes in position will be relevant to the following types of observations- Observerations with high astrometric requirements are probably already aware of issues with the accuracy of calibrator positions.
- The change in position can have an effect on observations where multiple
epochs are involved. If the nominal
position of the calibrator changes between the epochs, then this will
lead to a misregistration between the epochs. If the change in
nominal calibrator position is "significant" relative to the resolution
and the dynamic range requirements, then care is required. One
way to avoid these issues, where positional accuracy is of secondary
importance, is to continue to use the old calibrator positions.
To use the old positions, in SCHED select the old calibrator
catalogue as the default one with the command
defcat old_calibratorsNote the change in the calibrator catalogue does not affect schedule files that have already been developed.
The details
The names 0812-355, 1600-445 and 1729-373 have been removed from the catalogue. These names were alternatives of calibrators that remain in the catalogue.The following calibrators have been added: j0026-3512, j1147-6753, j1354-1041 and j1427-3306. These are new, and are of most relevance to 3mm observers.
The following table gives the list of calibrators whose position have been updated with improved ones, and the size of the change.
| Source | Change (milliarcsec) |
|---|---|
| 0002-478 | 201 |
| 0010-401 | 220 |
| 0023-263 | 180 |
| 0037-593 | 142 |
| 0048-447 | 321 |
| 0048-427 | 44 |
| 0107-610 | 840 |
| 0214-522 | 102 |
| 0235-618 | 97 |
| 0332-403 | 311 |
| 0355-669 | 546 |
| 0405-331 | 62 |
| 0414-341 | 191 |
| 0439-337 | 260 |
| 0448-392 | 263 |
| 0454-463 | 271 |
| 0534-340 | 82 |
| 0602-424 | 121 |
| 0610-436 | 173 |
| 0614-349 | 119 |
| 0615-365 | 91 |
| 0642-349 | 298 |
| 0727-365 | 154 |
| 0736-332 | 12 |
| 0745-330 | 231 |
| 0826-373 | 81 |
| 0906-682 | 207 |
| 0945-321 | 169 |
| 1012-44 | 47 |
| 1016-311 | 390 |
| 1022-66 | 135 |
| 1116-462 | 298 |
| 1151-348 | 109 |
| 1207-319 | 308 |
| 1320-446 | 6 |
| 1325-55 | 134 |
| 1327-311 | 20 |
| 1329-665 | 572 |
| 1412-368 | 243 |
| 1424-418 | 584 |
| 1450-338 | 119 |
| 1456-367 | 156 |
| 1458-391 | 229 |
| 1519-273 | 53 |
| 1554-64 | 36 |
| 1600-44 | 225 |
| 1604-333 | 188 |
| 1606-39 | 112 |
| 1607-841 | 232 |
| 1622-297 | 15 |
| 1624-61 | 93 |
| 1633-810 | 129 |
| 1657-56 | 72 |
| 1658-62 | 103 |
| 1729-37 | 107 |
| 1740-517 | 38 |
| 1814-637 | 29 |
| 1822-173 | 111 |
| 1823-455 | 155 |
| 1824-582 | 58 |
| 1827-360 | 47 |
| 1829-106 | 37 |
| 1854-663 | 493 |
| 1911+165 | 614 |
| 1950-613 | 15 |
| 1953-325 | 180 |
| 2002-375 | 291 |
| 2004-447 | 118 |
| 2030-689 | 209 |
| 2049-368 | 323 |
| 2052-474 | 443 |
| 2117-61 | 357 |
| 2117-642 | 283 |
| 2205-636 | 58 |
| 2215-508 | 161 |
| 2226-386 | 475 |
| 2244-372 | 1681 |
| 2254-367 | 121 |
| 2259-375 | 133 |
| 2311-452 | 12 |
| 2314-340 | 184 |
| 2321-375 | 5474 |
| 2322-411 | 56 |
| 2323-407 | 22577 |
| 2327-459 | 153 |
| 2337-334 | 1527 |
Original: Bob Sault (9-Oct-2005)
Modified: Bob Sault (9-Oct-2005)