Update for (131) Vala - May 25/26, 2002

Jan Manek's update

                    IOTA/IOTA-ES occultation update for
            (131) Vala / TYC 6812-00622-1 on May 25/26, 2002
     visible from Poland, Czechia, SE Germany, NW Austria, S Switzerland,
          N Italy, south France, north Spain and north Portugal


Summary 

In morning of the night of May 25/26, 2002 a faint 11.9 mag star TYC 6812-00622-1 will be occulted by a 43 km asteroid (131) Vala. This update is based on USNO/Flagstaff astrometry for the asteroid and UCAC1 star position.

The updated path shows ~2 path width south shift with time ~0.2 minutes earlier compared to Edwin Goffin's nominal prediction.

Updated path runs over Poland around 01:27 UT with Lodz and Warszawa in path at low altitude, Czechia around ~1:27.4 UT, nortwest Austria and southeast Germany with Munich on north limit ~1:27.7 UT, south Switzerland and very north Italy around 1:28.1 UT, south France aound 01:28.8 UT with Grenoble and Toulouse in path. Follows Pic du Midi observatory ~1:29.3 UT, north Spain ~1:29.8 UT and finally north Portugal with Porto on north limit ~1:30.6 UT. Please check the path chart for details.

Observation will be complicated by low altitude for observers in east Europe and a full Moon about 20 degrees west of this faint target star for all observers.

Clear sky and good luck !!!

The event at one glimpse:
 * date and approx. UT time of event: May 26, 2002 @ 01:28 UT
 * magnitude of target star: 11.9
 * magnitude drop [mag]: 1.3
 * estimated maximum duration [s]: 5.0
 * path description: given above
 * Goffin's original chart reference: A02_0516

The occultation path:
 * approximate ground width [km]: 100
 * uncertainty [path widths]: 1.4
 * uncertainty in time [s]: 10
 * 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 6812-00622-1
 * constellation: Ophiuchus
 * J2000 position [h,m,s; o,',"]: 17h 13m 59.7007s; -24o 07' 15.318"
 * position source: UCAC1
 * estimated accuracy ["]: 0.01" (0.012", 0.008")
 * V mag [mag]: 11.86
 * B-V [mag]: +0.35
 * remarks:
    Target star is in very south Ophiuchus, about 2.0 degrees NW of 3.3 mag star theta Ophiuchi = SAO 185320.
    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 GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 3.0x3.0 degrees
 * limiting magnitude is 12.5
 * labeled stars have indicated SAO numbers
 * remarks:





Data for the minor planet:
 * general information:
     number, name: (131) Vala
     approx. diameter [km]: 43
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone)
     number of used observations: 82 USNO
     number of rejected observations: 11 USNO
     time covered by the observations: 1998 03 10 - 2002 05 16
     rms residuals ["] (RA,DE): 0.07", 0.08"
     estimated positional accuracy at epoch of event ["]: 0.06", 0.05"
     remarks:

Data for the event:
 * UT date and time of least geocentric approach: 01:31.9 UT
 * approx. V mag of minor planet at event [mag]: 12.8
 * geocentric parallax of minor planet ["]: 6.807
 * magnitude drop [mag]: 1.3
 * estimated maximum duration [s]: 5.0
 * apparent motion of minor planet ["/h]: 32.72
 * angular distance to moon, phase of moon [deg,%]: 21, 100%
 * remarks:

Calculator(s): Jan Manek











Path coordinates:
                                                   Latitude   Latitude
                  Center               Altitude       Path Limits
  E. Longitude   Latitude      U.T.   star   sun   Limit 1    Limit 2
   ........................... shortened .............................
      o  '  "     o  '  "    h  m  s     o     o    o  '  "    o  '  "
     24  0  0    54 28 25    1 26 39     7    -5   55  8 24   53 49 47
     23  0  0    53 51 16    1 26 43     8    -6   54 30 31   53 13 18
     22  0  0    53 14 49    1 26 46     9    -6   53 53 22   52 37 29
     21  0  0    52 39  4    1 26 50    10    -7   53 16 58   52  2 21
     20  0  0    52  4  2    1 26 55    10    -8   52 41 18   51 27 53
     19  0  0    51 29 43    1 26 59    11    -9   52  6 22   50 54  7
     18  0  0    50 56  7    1 27  4    12   -10   51 32 12   50 21  2
     17  0  0    50 23 14    1 27  9    13   -11   50 58 46   49 48 40
     16  0  0    49 51  5    1 27 15    13   -11   50 26  6   49 16 60
     15  0  0    49 19 40    1 27 20    14   -12   49 54 11   48 46  2
     14  0  0    48 48 59    1 27 26    15   -13   49 23  2   48 15 47
     13  0  0    48 19  2    1 27 33    16   -14   48 52 38   47 46 15
     12  0  0    47 49 49    1 27 39    16   -15   48 22 59   47 17 26
     11  0  0    47 21 21    1 27 46    17   -15   47 54  6   46 49 21
     10  0  0    46 53 36    1 27 53    18   -16   47 25 59   46 21 58
      9  0  0    46 26 37    1 28  0    18   -17   46 58 37   45 55 20
      8  0  0    46  0 22    1 28  8    19   -17   46 32  0   45 29 24
      7  0  0    45 34 51    1 28 15    19   -18   46  6  9   45  4 13
      6  0  0    45 10  5    1 28 23    20   -19   45 41  4   44 39 45
      5  0  0    44 46  3    1 28 31    20   -20   45 16 44   44 16  1
      4  0  0    44 22 46    1 28 39    21   -20   44 53  9   43 53  0
      3  0  0    44  0 14    1 28 48    21   -21   44 30 20   43 30 43
      2  0  0    43 38 26    1 28 56    22   -21   44  8 16   43  9 10
      1  0  0    43 17 22    1 29  5    22   -22   43 46 57   42 48 21
      0  0  0    42 57  3    1 29 14    23   -23   43 26 24   42 28 16
   -  1  0  0    42 37 29    1 29 23    23   -23   43  6 35   42  8 54
   -  2  0  0    42 18 39    1 29 32    24   -24   42 47 32   41 50 16
   -  3  0  0    42  0 33    1 29 41    24   -24   42 29 14   41 32 22
   -  4  0  0    41 43 11    1 29 50    24   -25   42 11 41   41 15 12
   -  5  0  0    41 26 34    1 29 60    25   -25   41 54 53   40 58 45
   -  6  0  0    41 10 41    1 30  9    25   -26   41 38 49   40 43  2
   -  7  0  0    40 55 32    1 30 19    25   -26   41 23 31   40 28  2
   -  8  0  0    40 41  8    1 30 28    25   -27   41  8 57   40 13 47
   -  9  0  0    40 27 27    1 30 38    26   -27   40 55  8   40  0 14
   - 10  0  0    40 14 31    1 30 47    26   -28   40 42  3   39 47 26
   - 11  0  0    40  2 19    1 30 57    26   -28   40 29 44   39 35 21
   - 12  0  0    39 50 50    1 31  7    26   -28   40 18  8   39 23 59
   ........................... 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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