Update for (101) Helena - March 31, 2003 - South Africa

Jan Manek's update

                    IOTA/IOTA-ES occultation update for
               (101) Helena / TYC 1930-00271-1 on March 31, 2003
    visible from SW Angola, NE Namibia, SW Botswana and middle South Africa


Summary 

In the evening of March 31, 2003 a faint 11.2 mag star TYC 1930-00271-1 will be occulted by a 68 km asteroid (101) Helena. This update is based on USNO/Flagstaff for the asteroid and recent UCAC star position.

The updated path shows ~1 path width north shift with time 0.5 minutes later compared to Edwin Goffin's nominal prediction.

Updated path runs over SW Angola ~17:36 UT, NE Namibia ~17:37 UT, SW Botswana ~17:38 UT and middle South Africa around 17:39.2 UT with Port Elisabeth in path ~17:39.8 UT. Please check the path chart for details.

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 31, 2003 @ 17:39 UT (S.Africa)
 * magnitude of target star: 11.2
 * magnitude drop [mag]: 2.3
 * estimated maximum duration [s]: 8.7
 * path description: given above
 * Goffin's original chart reference: A03_0313

The occultation path:
 * approximate ground width [km]: 85
 * uncertainty [path widths]: 1.2
 * uncertainty in time [s]: 11
 * map: below
 * remarks: Path uncertainties are given according to nominal star
    position errors and expected asteroid positional accuracy.

Data for the target star:
 * name: TYC 1930-00271-1
 * constellation: Cancer
 * J2000 position [h,m,s; o,',"]: 08h 03m 01.0599s; +26o 03' 15.847"
 * position source: recent UCAC position combined with Tycho-2 proper motion
 * estimated accuracy ["]: 0.03" (0.03", 0.02")
 * V mag [mag]: 11.22
 * B-V [mag]: +0.68
 * remarks:
    Target star is in northwest Cancer, about 4.4 degrees east of 1.2 mag star beta Geminorum = Pollux = SAO 79666.
    !!! 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: (101) Helena
     approx. diameter [km]: 68
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone)
     number of used observations: 94 USNO
     number of rejected observations: 21 USNO
     time covered by the observations: 1998 11 27 - 2003 03 11
     rms residuals ["] (RA,DE): 0.05", 0.04"
     estimated positional accuracy at epoch of event ["]: 0.04", 0.04"
     remarks:

Data for the event:
 * UT date and time of least geocentric approach: 17:31.1 UT
 * approx. V mag of minor planet at event [mag]: 13.4
 * geocentric parallax of minor planet ["]: 3.543
 * magnitude drop [mag]: 2.3
 * estimated maximum duration [s]: 8.7
 * apparent motion of minor planet ["/h]: 15.66
 * angular distance to moon, phase of moon [deg,%]: 119, 1%
 * remarks:

Elements for WinOccult:
============ cut here ===========================================
 2003 Mar 31
 101  Helena
17h 31.1m UT
  11.2    8  3  1.060 26  3 15.85TYC 1930-00271-1      11.9
13.4     68    8.7   2.482     0.758    -11.89
   29.290  26.057   -81.72    4.19
 17.5190  -.43850  -.37464  2.87855 -3.35566  0.00542 -0.00130
2000    158.5652622003 322.00000347.328121343.49252710.196378 0.140282872.585281732.222611008.335   0.35
RATE 2.3710580 .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  '  "
                                                        Longitude  Longitude
     13 53 22   -12  0  0   17 35 12    50    20    -7   13 26 13   14 20 22
     14 32 31   -13  0  0   17 35 28    49    19    -8   14  5 29   14 59 24
     15 10 48   -14  0  0   17 35 44    48    18    -9   14 43 53   15 37 35
     15 48 17   -15  0  0   17 35 59    47    16   -10   15 21 27   16 14 59
     16 24 59   -16  0  0   17 36 14    47    15   -10   15 58 13   16 51 38
     17  0 58   -17  0  0   17 36 29    46    14   -11   16 34 15   17 27 34
     17 36 15   -18  0  0   17 36 43    45    13   -11   17  9 34   18  2 49
     18 10 53   -19  0  0   17 36 57    44    12   -12   17 44 12   18 37 27
     18 44 54   -20  0  0   17 37 11    43    11   -13   18 18 13   19 11 28
     19 18 20   -21  0  0   17 37 25    42    10   -13   18 51 37   19 44 55
     19 51 12   -22  0  0   17 37 38    41     9   -14   19 24 27   20 17 50
     20 23 32   -23  0  0   17 37 51    41     9   -14   19 56 44   20 50 14
     20 55 23   -24  0  0   17 38  4    40     8   -15   20 28 30   21 22  8
     21 26 44   -25  0  0   17 38 16    39     7   -15   20 59 47   21 53 35
     21 57 38   -26  0  0   17 38 28    38     6   -16   21 30 35   22 24 36
     22 28  7   -27  0  0   17 38 40    37     6   -16   22  0 56   22 55 11
     22 58 11   -28  0  0   17 38 51    36     5   -17   22 30 52   23 25 23
     23 27 52   -29  0  0   17 39  2    35     4   -17   23  0 24   23 55 13
     23 57 10   -30  0  0   17 39 13    34     4   -17   23 29 32   24 24 42
     24 26  8   -31  0  0   17 39 24    33     3   -18   23 58 19   24 53 51
     24 54 45   -32  0  0   17 39 34    32     2   -18   24 26 45   25 22 41
     25 23  4   -33  0  0   17 39 44    31     2   -18   24 54 50   25 51 13
     25 51  5   -34  0  0   17 39 53    30     1   -19   25 22 37   26 19 28
     26 18 49   -35  0  0   17 40  2    29     1   -19   25 50  6   26 47 27
     26 46 17   -36  0  0   17 40 11    28     0   -19   26 17 17   27 15 12
  ............................. 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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