Update for (747) Winchester - March 28/29, 2003

Jan Manek's update

                    IOTA/IOTA-ES occultation update for
           (747) Winchester / TAC +04 11674 on March 28/29, 2003
 visible from Morocco, E Spain, France, W Belgium, W Netherlands and SW Norway

Summary 

In the morning of night of March 28/29, 2003 a faint 11.3 mag star TAC +04 11674 will be occulted by a 178 km asteroid (747) Winchester. This update is based on USNO/Flagstaff, TMO and Bordeaux-Floirac astrometry for the asteroid and recent UCAC star position.

The updated path shows ~7 path width west shift with time 3.5 minutes earlier compared to Edwin Goffin's nominal prediction.

Updated path runs over Morocco around 4:23 UT, E Spain ~4:25.2 UT, France around 4:26.6 UT, W Belgium ~4:27.4 UT, W Netherlands ~4:27.6 UT and SW Norway around 4:28.8 UT under strong morning twilight. Please check the path chart for details.

Large difference compared to nominal prediction is caused mainly by new star position provided by UCAC team. The TAC position is off ~0.8" mainly in declination compared to UCAC. I have checked DSS images and found no clear evidence of duplicity that could affect UCAC astrometry, there is only a hint of very faint star on east side of the star, which couldn't affect UCAC in declination. I have therefore decided that UCAC is correct (internal accuracy is stated to be 9 and 8 mas from 6 images showing no field for any scatter) and rejected both TAC position and proper motion. Using AC 2000.2 as first epoch astrometry permitted deriving new proper motions which were later applied to get the final target star position.

This update was computed with a Beta version of Winoccult, so you can notice a slightly different path chart header and more items in table of path limits (still more columns to appear there in future). OCCELMNT files should be compatible. Clear sky and good luck !!!

The event at one glimpse:
 * date and approx. UT time of event: March 29, 2003 @ 04:26 UT (Europe)
 * magnitude of target star: 11.3
 * magnitude drop [mag]: 3.0
 * estimated maximum duration [s]: 24.6
 * path description: given above
 * Goffin's original chart reference: A03_0344

The occultation path:
 * approximate ground width [km]: 200
 * uncertainty [path widths]: 0.9
 * uncertainty in time [s]: 23
 * map: below
 * remarks: Path uncertainties are given according to nominal star
    position errors and expected asteroid positional accuracy.

Data for the target star:
 * name: TAC +04 11674 = GSC 5074-0192
 * constellation: Ophiuchus
 * J2000 position [h,m,s; o,',"]: 17h 18m 25.7943s; -04o 17' 51.403"
 * position source: recent UCAC position combined with derived proper motion
 * estimated accuracy ["]: 0.04" (0.02", 0.03")
 * V mag [mag]: 11.25 according to TAC
 * B-V [mag]: +0.6 ?  estimate
 * remarks:
    Target star is in central Ophiuchus, about 2.2 degrees WNW of 4.5 mag star SAO 141665
    or 8' west of 8.0 mag star SAO 141603.
    The TAC position is off ~0.8" mainly in declination compared to UCAC. I have checked DSS images and found no clear evidence
    of duplicity that could affect UCAC astrometry, there is only a hint of very faint star on east side of the star, which
    wouldn't affect UCAC in declination. I have therefore decided that UCAC is correct (internal accuracy is stated to be 9 and 8 mas
    from 6 images showing no field for any scatter) and rejected both TAC position and proper motion. Using AC 2000.2 as first epoch
    astrometry permitted deriving new proper motions which were later applied to get the final target star position.
    !!! IMPORTANT !!!
    Purple stars in identification chart are so called 'non-star' objects in GSC; in dense fields
    the 'non-stars' are often real stars or blends of close pairs. Be careful about this.

Close finding chart (prepared in GUIDE8):
 * occulted star is in center - labeled with cross
 * field is 3.0x3.0 degrees
 * limiting magnitude is 13.0
 * labeled stars have indicated SAO numbers
 * remarks: Second chart is 30' blowup to show correctly the target star in the field.











Data for the minor planet:
 * general information:
     number, name: (747) Winchester
     approx. diameter [km]: 178
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen), Bordeaux-Floirac
     number of used observations: 135 USNO, 30 TMO, 2 Bordeaux-Floirac
     number of rejected observations: 19 USNO, 3 TMO
     time covered by the observations: 1989 11 19 - 2002 07 01
     rms residuals ["] (RA,DE): 0.08", 0.08"
     estimated positional accuracy at epoch of event ["]: 0.06", 0.06"
     remarks: No recent opposition astrometry.

Data for the event:
 * UT date and time of least geocentric approach: 04:17.0 UT
 * approx. V mag of minor planet at event [mag]: 14.2
 * geocentric parallax of minor planet ["]: 2.510
 * magnitude drop [mag]: 3.0
 * estimated maximum duration [s]: 24.6
 * apparent motion of minor planet ["/h]: 10.25
 * angular distance to moon, phase of moon [deg,%]: 71, 12%
 * remarks:

Elements for WinOccult:
============ cut here ===========================================
 2003 Mar 29
 747  Winchester
 4h 17.0m UT
  11.3   17 18 25.794- 4 17 51.40TAC +04 11674         11.9
14.2    178   24.6   3.504     0.324      9.03
    9.189  -4.300  -243.00    3.20
  4.2836  -.37182   .20079  1.93720  3.59534 -0.00568 -0.00018
2000    211.9756452003 322.00000275.637708130.21019318.178950 0.344746892.992484301.960834637.695   0.15
RATE 1.9039530 .0000000 .0000000 .0000000 .00000000 .00000000 .00000000
============ cut here ===========================================

Calculator(s): Jan Manek









Path coordinates:
                  Centre              Star  Star   Sun      Path Limits
  E. Longitude   Latitude      U.T.    Alt    Az   Alt    Limit 1    Limit 2
      o  '  "     o  '  "    h  m  s     o     o     o    o  '  "    o  '  "
                                                         Latitude   Latitude
  ............................. shortened ..................................
      o  '  "     o  '  "    h  m  s     o     o    o  '  "    o  '  "
   -  5  0  0    27 36 15    4 22 25    56   157   -25   24 44 40   30 40  2
   -  4  0  0    30 29 22    4 23  7    54   160   -23   27 31 11   33 41  8
   -  3  0  0    33 24 55    4 23 48    51   163   -21   30 20  8   36 44 48
   -  2  0  0    36 21 53    4 24 28    49   166   -20   33 10 34   39 49 57
   -  1  0  0    39 19  7    4 25  7    46   168   -18   36  1 28   42 55 19
      0  0  0    42 15 24    4 25 43    43   170   -16   38 51 43   45 59 31
      1  0  0    45  9 28    4 26 17    40   172   -14   41 40 10   49  1  8
      2  0  0    47 59 59    4 26 49    38   174   -12   44 25 39   51 58 39
      3  0  0    50 45 43    4 27 17    35   176   -11   47  7  3   54 50 36
      4  0  0    53 25 29    4 27 43    32   177    -9   49 43 18   57 35 37
      5  0  0    55 58 14    4 28  6    30   178    -8   52 13 28   60 12 26
      6  0  0    58 23  7    4 28 26    27   180    -7   54 36 47   62 40  0
      7  0  0    60 39 28    4 28 44    25   181    -5   56 52 38   64 57 31
      8  0  0    62 46 50    4 28 59    23   182    -4   59  0 36   67  4 29
      9  0  0    64 45  0    4 29 12    21   183    -3   61  0 25   69  0 42
     10  0  0    66 33 59    4 29 22    19   184    -3   62 52  3   70 46 14
  ............................. shortened ..................................

----------------------------------------------------------------------------
Jan Manek
Stefanik Observatory                Private :
Petrin 205                          Werichova 950
118 46  Praha 1                     152 00  Praha 5 - Barrandov     |_|_|
Czech Republic                      Czech Republic                  /   \
Internet : jan.manek@worldonline.cz                                |-O-O-|
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