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[vsnet-chat 325] Re: V1830 Sagittarii

Stan Walker wrote in [vsnet-chat 323]:

> Their stated limit is 14 on this chart and they identify a star
> about 40" south of a star of about magnitude 10.  This star is mag 14 if
> their limit is accurate - the limit looks rather fainter to me. 

   I think the DSS-based chart by Downes and Shara reaches much deeper than
mag 14 (at least for Downes and Shara 1993).

> My problem is that I have a star of mag 12 about 10" south of the tenth
> magnitude star and nothing where Downes & Shara put V1830. May 16 & 17 UT.
> They don't show this twelfth magnitude star. Is It V1830? Or has it now
> returned to normal? I'd like to make sense of the CCD frames I have.

    Giving J2000.0 coordinates of the suspected outbursting object will
improve the situation and help other observers.  It might still be possible
the true V1830 Sgr differs from the quoted faint counterpart in several
literatures.  According to the VSNET chart (position based on Downes and
Shara 1993), the star just north of the variable has a V magnitude of
12.55.  Does the "tenth magnitude star" correspond to this?  I suspect
the earlier published range of magnitude of V1830 Sgr was heavily contaminated
by this star.

    Attached is the relevant VSNET chart.

Regards,
Taichi Kato


  * observer: T. Kato (Ouda Station, Kyoto University)
  * calibration: N. Vogt (1977) Publ. VSS RASNZ
  * identification: astrometric position from Downes & Shara (1993)
                    (a little approximate)

    181351     -274232      2000 V1830 Sgr  UG           11.5-17.5p

------------------------------------------------------------------
frame DD84677   600 V1830 Sgr            V         
date 96  3 15.84700  (V mag)
 449 17552 1222 0 
 543 10852 1505 0 
 627 19032 1553 0 
 888 7891 1097 0 
 1164 2514 1370 0 
 1128 23236 1409 0 
 1675 17333 1227 0 
 1595 19410 1362 0 
 1619 26771 1462 0 
 1796 4817 1346 0 
 1832 22507 1489 0 
 2010 25158 1370 0 
 2245 3286 1380 0 
 2353 8006 1499 0 
 2160 20251 1506 0 
 2271 24389 1551 0 
 2434 6319 1257 0 
 2418 19053 1499 0 
 2657 4822 1421 0 
 2776 10900 1539 0 
 2758 11991 1499 0 
 2763 19729 1526 0 
 2936 26764 1442 0 
 3199 16040 1381 0 
 3461 7715 1482 0 
 3533 24025 1440 0 
 3450 26849 1323 0 
 3607 17030 1465 0 
 3581 27934 1422 0 
 3760 14652 1486 0 
 3689 19396 1533 0 
 3805 21007 1405 0 
 4163 25527 1471 0 
 4689 12037 1532 0 
 4784 16216 1547 0 
 4860 25019 1498 0 
 5113 5511 1507 0 
 5110 9594 1353 0 
 5316 24333 1454 0 
 5416 27756 1449 0 
 5607 15173 1434 0 
 5527 16282 1360 0 
 5750 4417 1427 0 
 5638 23738 1404 0 
 5817 5953 1494 0 
 6042 13004 1471 0 
 6037 20310 1441 0 
 6239 17441 1442 0 
 6519 9917 1417 0 
 6782 12777 1486 0 
 6850 18973 1445 0 
 6890 6748 1475 0 
 6892 17146 1273 0 
 7411 21976 1457 0 
 7912 10758 1507 0 
 7902 27838 1543 0 
 8054 8817 1416 0 
 8181 11907 1524 0 
 8064 15225 1469 0 
 8058 21496 1457 0 
 8205 4090 1375 0 
 8410 2776 1421 0 
 8274 13075 1508 0 
 8348 5471 1495 0 
 8464 18801 1387 0 
 8632 4668 1460 0 
 8850 6806 1328 0 
 9061 24341 1371 0 
 9200 20860 1460 0 
 9305 8808 1470 0 
 9299 26987 1471 0 
 9510 4758 1438 0 
 9448 7730 1493 0 
 9636 6390 1467 0 
 9709 22001 1368 0 
 9707 25170 1504 0 
 9779 14027 1441 0 
 9909 24320 1462 0 
 10090 28177 1424 0 
 10117 11927 1530 0 
 10180 17474 1343 0 
 10586 4787 1315 0 
 10686 11064 1362 0 
 10888 14730 1483 0 
 10959 7571 1517 0 
 10979 20080 0 1 V1830 Sgr
 11027 18331 1362 0 
 11332 16137 1541 0 
 11237 19142 1255 0 
 11417 11620 1525 0 
 11483 2503 1513 0 
 11591 5525 1512 0 
 11703 27951 1448 0 
 11669 4434 1549 0 
 11584 14306 1556 0 
 11676 25820 1430 0 
 11875 15747 1465 0 
 12161 18354 1410 0 
 12320 9143 1418 0 
 12318 24954 1407 0 
 12501 3120 1501 0 
 12344 24295 1504 0 
 12417 25981 1470 0 
 12573 21802 1537 0 
 12638 6210 1470 0 
 12720 11648 1534 0 
 13002 3688 1402 0 
 13099 5111 1434 0 
 13331 9566 1415 0 
 13389 10311 1370 0 
 13600 21965 1372 0 
 13959 7811 1388 0 
 14201 11788 1401 0 
 14080 19578 1387 0 
 14215 14774 1492 0 
 14374 12662 1537 0 
 14524 6086 1426 0 
 14455 2487 1561 0 
 14723 7325 1496 0 
 14731 16387 1031 0 (1031)
 15119 26730 1454 0 
 15276 5964 1501 0 
 15355 7956 1406 0 
 15445 9818 1521 0 
 15612 18684 1449 0 
 15763 22954 1431 0 
 15859 16363 1358 0 
 16227 8953 1234 0 
 16155 22316 1430 0 
 16174 24119 1449 0 
 16211 27969 1433 0 
 16393 14025 1526 0 
 16654 5683 1294 0 
 16755 21653 1558 0 
 16924 10863 1465 0 
 17202 12872 1447 0 
 17000 19997 1557 0 
 17206 24961 1520 0 
 17282 15553 1438 0 
 17505 3667 1455 0 
 17394 23645 1422 0 
 17655 22181 1347 0 
 17907 11527 1495 0 
 18052 18031 1469 0 
 18213 8229 1458 0 
 18031 14981 1356 0 
 18158 8962 1458 0 
 18423 20818 1443 0 
 18389 27922 1291 0 
 18438 3930 1488 0 
------------------------------------------------------------------

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